Currently, almost 80% of the world's population, primarily in Africa and other poor countries, rely entirely on traditional or herbal medicine for disease treatment. While numerous chemicals originating from traditional medicinal plants have made their way into present pharmaceutical practises as a result of considerable research and development of drugs, there are still a number of plants with potential therapeutic value that remain mainly undiscovered. The study aimed at analysing the phytochemical profile of Paulownia elongata root and bark extract using Gas Chromatography-Mass Spectrometry (GC-MS) and evaluating its antibacterial potential. The roots of P. elongata were collected, dried, and extracted with methanol. The extracted compounds analyzed by GC-MS revealed the presence of 20 chemical/bioactive constituents. The major compounds identified were theobromine, oleic acid, oxime-methoxyphenyl, and methyl stearate. The antibacterial activity of the extract was assessed against four bacterial strains: Staphylococcus aureus, Pseudomonas aeruginosa, Clostridium bolulinum, and Escherichia coli. The well method of the agar dilution was used to determine the antibacterial activity, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. The results showed that methanolic extract of P. elongata roots exhibited significant antibacterial activity against the tested bacterial strains, with varying degrees of inhibition. The antibacterial potential of the roots extract showed higher activity at 300 mg/kg/bwt with 18.12+0.9 mm on Salmonella typhi and at 400 mg/kg/bwt with inhibition rate 20.14+ 0.0 mm on Klebsiella pneumonia. From the findings of this study, P. elongata root extract contains bioactive compounds and possesses antibacterial potential. These findings support the traditional use of Paulownia species in traditional medicine and highlight its potential as a source of novel antibacterial agents. Further research is warranted to isolate and characterize the active compounds and investigate their mechanisms of action.

Keywords: phytochemicals, Paulownia elongate, medicinal plants, gram positive bacteria, gram negative bacteria

Medicinal plants have been used to cure a variety of illnesses in African traditional medicine as well as other cultures throughout the world.^1,2 Currently, almost 80% of the world's population, primarily in Africa and other poor countries, rely entirely on traditional or herbal medicine for disease treatment³ While numerous chemicals originating from traditional medicinal plants have made their way into present pharmaceutical practises as a result of considerable research and development of drugs, there are still a number of plants with potential therapeutic value that remain mainly undiscovered.⁴

Paulownia is a woody tree well renowned for its timber quality, but its medicinal benefits are just recently being discovered. The genus Paulownia, belonging to monogeneric Paulowniaceae family, comprises of nine species: Paulownia. albiphloea (P. albiphloea), Paulownia australis (P. australis), Paulownia catalpifolia (P. catalpifolia), Paulownia elongata (P. elongata), Paulownia fargesii (P. fargesii), Paulownia fortunei (P. fortunei), Paulownia kawakamii (P. kawakamii), Paulownia taiwaniana (P. taiwaniana), and Paulownia tomentosa (P. tomentosa). Despite being extensively spread across China, most Paulownia species have been planted and farmed in many places throughout the world for their decorative and wood benefits.^5,6 Paulownia wood is light and flexible, yet it does not fracture or deform readily. It is valued for its structural resilience, textures (light to medium clay-sandy), grain, and colour⁵. The wood is very resistant to moisture and possesses flame retardant qualities.⁷ Furthermore, being a short rotation rapid growing tree, Paulownia has already gained interest as a possible bioenergy crop capable of both carbon sequestration and transportation fuel production.^8,9

In terms of plant components utilised in traditional medicine, Paulownia happens to be one of the most used medicinal plants. In traditional Chinese medicine, the bark, fruit, xylem, and leaves of P. tomentosa var. tomentosa have been utilised for the treatment or prevention of a wide range of diseases, such as haemorrhoid, carbuncle, inflammatory bronchitis, gonorrhoea, upper respiratory tract infection, parotitis, asthma, traumatic bleeding, erysipelas, bacteriological diarrhoea, swelling, bronchopneumonia, enteritis, conjunctivitis, hypertension, and tonsillitis.^10,11 P. tomentosa leaves, wood, and fruits have traditionally been used to treat tonsillitis, bronchitis, asthmatic attacks, and bacterial diseases such as enteritis or dysentery. The leaves of Paulownia have been used to treat frostbite and leg ulcers, thus they may offer wound-healing capabilities as well.¹² The most significant plant components used in traditional herbal therapy are leaves, fruits, and flowers.^13,14 In Chinese folk medicine, mashed Paulownia flowers are used to cure acne vulgaris, and the decoction is used to treat fungal infections on the sole of the foot and the area between the toes.¹⁵ Flowers have also been utilised to treat first and second degree empyrosis.¹⁶ The goal of this study is to use Gas Chromatography-Mass Spectrometry (GC-MS) analysis to identify the phytochemical profile of Paulownia elongate roots extract and evaluate its antibacterial potential as a medicinal plant.

Plant collection

The roots of P. elongata were collected from Wukari Local Government Area of Taraba State. It was washed under running water with an intensive care and was air-dried for about 5 weeks for easy grinding. Identification and authentication were done at the herbarium in the Department of Plant Sciences of Modibbo Adama University Yola, Nigeria.

Plant extraction

The air-dried roots of P. elongata were grinded to a smooth powdered form. Then 150g of the sample (roots of P. elongata) was weighed with an analytical weighing balance and put into a 1000mL container. 800mL of methanol was then added into the 1000mL container and was left for 48 hours for proper absorption. After 48 hours, the liquid sample was extracted and was evaporated in a water thermostat.

Test organisms

Clinical isolates of four bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, and Clostridium Bolulinum and Escherichia coli.) were obtained from the Modibbo Adama University Yola Adamawa State, Nigeria. The bacteria were kept at 40°C on Nutrient agar slant. Before usage, the isolates were subcultured on new medium at regular intervals. Martins et al.¹⁷ established a method for standardising inocula.

Antibacterial assay

The antibacterial activity of plant extracts was determined using the well technique of agar dilution. Mueller Hinton Agar (MHA) was carefully put into the petri plates and allowed to set. After punching holes (i.e. 5 wells) in the infected agar using a sterile 8mm cork borer, the agar was removed. Four wells were filled with varying concentrations of extracts and marked as follows: 100mg/ml, 50mg/ml, 25mg/ml, and 12.5mg/ml, while the fifth well contained the extractant, i.e. the solvent used for the extraction, to serve as a control. The bacterial cultures were injected on Mueller Hinton Agar (MHA) and incubated for 24 hours at 370°C. Following incubation, the diameter of the zone of inhibition around each well was measured to the approximate millimeters.

Determination of the minimum concentration of extracts (MIC)

The MIC of the plant methanolic extracts was determined using the agar diffusion method described by Baker and Breach¹⁸: one millilitre of each extract was added to about 14ml of nutrient agar to make a final concentration ranging from 12.5% w/v to 100% w/v of the extracts in the agar. Standardised inocula were streaked on agar in petri plates with varied extract concentrations. The plates were incubated for 24 hours at 370°C. The MIC was determined by taking the lowest dose of each extract that inhibited the growth of the test organism.

Determination of bactericidal and bacteriostatic effects of the extracts

The Minimum Bactericidal Concentration (MBC) was determined by visual observation of growth suppression in solid medium. After 24 hours of incubation at 370C, the agar plates of various extracts of varied concentrations inoculated with organisms were inspected for growth. Plates with no obvious growth were subcultured on new nutrient agar plates by selecting inocula from the streaking line. The smallest bactericidal concentration was determined to be the smallest quantity of the extract that did not generate any growth on the solid medium following incubation.

Gas chromatography-mass spectrometry (GC-MS) analysis

Phytochemical screening was done in order to detect the presence of plant constituents. 1µL of the crude extract dissolved in methanol of GC MS grade was subjected to the GC MS for the profiling of the chemical constituents. The GC-MS analysis was performed on a combined 7890A gas chromatograph system (Agilent 19091-433HP, USA) and mass spectrophotometer, which was outfitted with an HP-5 MS fused silica column (5% phenyl methyl siloxane 30.0 m250 m, film thickness 0.25 m), and interfaced with a 5675C Inert MSD with Triple-Axis detector. Helium gas was employed as the carrier gas, with a column velocity flow of 1.0 mL min-1. Other GC-MS settings include 250°C ion-source temperature, 300°C interface temperature, 16.2 psi pressure, 1.8 mm out time, and a 1 L injector in split mode with a split ratio of 1:50 and injection temperature of 300°C. The column temperature began at 36°C for 5 minutes and increased to 150 V at a rate of 4°C min-1. The temperature was increased to 250°C at a rate of 20°C min-1 and kept for 5 minutes. The entire time for elution was 47.5 minutes. The relative percent quantity of each component was computed by comparing the mean peak area with the entire areas. The supplier's MS solution software was utilised to operate the system and collect the data.

GC-MS chromatogram and phytochemical profile of Paviownia elongata root-bark methanol crude extract

The study determined the phytochemical profile of methanolic extracts of paulownia elongate roots using GC-MS as displayed in the chromatogram (Figure 1). The plant (paulownia elongata) was utilized in this study due to its bioactive ingredients and has proven its medicinal important. The methanolic aqueous extracts of paulownia elongate roots showed that the extract contains many chemicals and where varied according to their retention time, peak area, height and base (Table 1). The highest compound identified was theobromine (34.42%), oleic acid (37.87%), followed by oxime, methoxy-phenyl (3.32%) and methyl stearate (4%). The least compounds identified were ethanol, 2-(hexyloxy) and alpha-pineme (1.19%).

Figure 1 GC-MS chromatogram of Paviownia elongata Root-bark methanol crude extract.

Some of the chemical composition isolated from the methanolic roots of paulownia elongata includes; p-Cymene, tetradecanoic acid, Maltol, Dodecanal, Hydroperoxide,1-ethylbutyl, alpha.-phellandrene, alpha-pineme, Ethanol, 2-(hexyloxy)-, Theobromine, octadecadonic acid, E,Z-5,7-Dodecatrien-1-ol acetate,  2,6,10-Dodecatrien-1-ol, methyl stearate. Some of these compounds, particularly acids, have been shown to be bioactive.

Effect of Paviownia elongata roots methanol crude extract (µg/mL) on Gram positive and Gram-negative bacteria in millimetre (mm)

The presence of phytochemicals in Paulownia elongate roots may indicate the plant's potential in the management of diseases associated with free radical buildup in the body, such as diabetes mellitus, as well as anticancer, anti-mutagenic, antifungal, and antibacterial properties. When compared to the test controls, the results reveal a great inhibition rate against the tested species of bacteria at 30g concentration. The antibacterial efficacy against all species, however, was decreased (Table 2). The inhibition obtained at various doses (100-300 g) was shown to be effective across all of the strains tested.

Result is Mean + SD.  N = 3

 *, significant activity was observed when compared to the control (p<0.05);    Concentration of standard is 30 µg/mL of tetracycline, Conc, concentration

The extract showed higher significant antibacterial activity against Escherichia coli, and salmonella typhi at 100µg and 300µg with an inhibition rate of 18.13±i.6 and 18.12±0.9 respectively and the extract also showed a significant antibacterial activity on klebsiella pneumonia 100 µg and 300µg with an inhibition rate of 17.16±0.12 and 15.14±0.5.

The investigation of chemical compounds of the genus Paulownia began in the early 1930s. The initial researchers in this discipline were Japanese. Investigations on herbal remedies from the genus Paulownia strive to uncover novel compounds using methodologies and current spectroscopic techniques (Table 3). Iridoid glycosides, phenyl-propanoid glycosides, lignin glycosides, flavonoids, sesquiterpenes, and triterpenes are the most prominent. A majority of the aforementioned substances have been shown to exhibit some level of bioactivity.¹⁹ Recently, phenylethanoid derivatives integrated via ether or ester link to iridoid glycosides have been discovered.²⁰ Campneosid I phenylethanoid glycosides isolated from P. tomentosa exhibit strong biological activity. Campneosid I was shown to exhibit considerable antibacterial action against a variety of pathogenic Streptococcus and Staphylococcus species, including S. aureus.²¹

Glycosides are a broad and important family of carbohydrate molecules that are distinguished by the substitution of another substituent for the anomeric hydroxyl group.²² Research on plant-based substances from the genus Paulownia promise to disclose novel compounds as chromatographic procedures and advanced spectroscopic techniques progress. Iridoid glycosides, phenyl-propanoid glycosides, lignin glycosides, flavonoids, sesquiterpenes, and triterpenes are the most prominent. Many of these compounds have been shown to exhibit some level of bioactivity.¹⁹ Recently, phenylethanoid derivatives integrated via ether or ester link to iridoid glycosides have been discovered.²⁰ Campneosid I phenylethanoid glycosides isolated from P. tomentosa exhibit strong biological activity. Campneosid I was shown to exhibit considerable antibacterial action against a variety of pathogenic Streptococcus and Staphylococcus species, including S. aureus.²¹

Lignin study of Paulownia wood revealed the presence of syringin, a bioactive chemical.²¹ Syringin is a phenylpropanoid glycoside derived from eleutheroside. Free radical harvesting, neuronal cell damage preventative measures, apoptosis suppression, antidiabetic impact, anti-inflammatory prospects, antinociceptive impact, and anti-allergic effects are among the pharmacological features of syringin.¹⁸ Furthermore, Paulownia has been shown to be insect-resistant, neuroprotective, antioxidant, and hemostatic.¹⁹

Flavonoids are a class of hydroxylated polyphenolic chemicals with a benzo--pyrone structure that are abundant in plants. The phenylpropanoid pathway produces these. Secondary phenolic metabolites, including flavonoids, are synthesised in response to diverse stress circumstances and have a variety of pharmacological actions^22,23,24. Flavones, flavanones, catechins, and anthocyanins are the four major types of flavonoids.²⁵ P. tomentosa geranylated flavanone has been demonstrated to reduce nitrite oxide levels in LPS-stimulated rat macrophages.²⁶ Tomentodiplacone B (TOM B), on the other hand, suppressed the growth of human moncytic leukaemia cells.²⁷

The flowers appear to be the most utilised plant component among diverse sections of the Paulownia tree, with many uses in traditional medicinal products.^28,29 Because of the presence of flavonoids, notably Apigenin, extracts of P. tomentosa flowers have piqued the interest of researchers. Apigenin is hypotensive,³⁰ antispasmodic,³¹ antiinflammatory,³² vasorelaxant³³ and antioxidant.³⁴ Furthermore, apigenin has been shown to have anti-tumorigenic properties both in vitro and in vivo, not only by inhibiting tumour cell proliferation but also by impairing tumour cell invasiveness.^35,36

Flavonoids extracted from P. tomentosa leaves are being shown to exhibit antiradical and cell protecting properties.³⁷ In vitro antibacterial activity of fresh P. elongata leaves and silage extracts against Pseudomonas aeruginosa, Salmonella enterica, Candida albicans, Staphylococcus aureus, Streptococcus pyogenes and Paenibacillus alvei. Popova and Baykov (2013) found that the inhibitory impact is stronger against gram-negative bacteria. In in vitro tests on cervical and breast cancer cell lines, the leaves of P. tomentosa (misidentified as P. coreana) contained isoatriplicolide tiglate (PCAC), which triggered apoptosis.³⁸ Varlyakov et al.³⁹ investigated the effect of P. elongata leaf consumption on blood parameters in three yearling sheep, Stara Zagora x Pleven Blackhead hybrids. Their findings demonstrated a considerable decline in erythrocyte and leukocyte counts, with the most marked decrease occurring in the postprandial hours. Furthermore, their research revealed that the leaves of P. elongata had the capacity to drastically lower blood glucose levels.

Paulownia flower extracts limit the development of some bacteria, with the highest impact reported on Staphylococcus aureus and having a smaller impact on Penicillium chrysogenum, Saccharomyces cerevisiae, and Aspergillus niger.⁴⁰ Methanol extracts of P. tomentosa dried flowers have been demonstrated to exhibit antiviral activity over Coxsackie virus A16 (CAV 16) and enterovirus 71 (EV 71), the two primary pathogens causing hand, foot, and mouth disease (HFMD).⁴¹ Ibrahim et al.⁴² discovered that essential oils extracted from P. tomentosa flowers have broad range antibacterial action against Escherichia coli NRRL B-210, Staphylococcus aureus NRRL B-313, and Bacillus subtilis NRRL B-543.

Certain chemicals found in Paulownia fruits have been shown to have strong inhibitory effect towards Staphylococcus epidermidis, a pathogenic gram-positive bacterium.⁴³ According to one research, the fruits of P. tomentosa can be a viable source of naturally occurring antioxidant compounds.⁴⁴ Purification of the methanol extract of P. tomentosa fruits resulted in potent butyrylcholinesterase (BChE) and acetylcholinesterase (hAChE) inhibitory flavonoids, which have been linked to the amelioration of Alzheimer's symptoms, as well as a rich source of many different geranylated flavonoids.⁴⁵ The antibacterial activity of compounds 3’O-methyldiplacol, mimulone D, tomentodiplacone D, tomentodiplacone G, 3’-Omethyl-5’-hydroxydiplacone, mimulone C,  tomentodiplacone B, diplacone, 3’-O-methyl-5’O-methyldiplacone, tomentodiplacone E mimulone, and tomentodiplacone C against different Methicillin-resistant Staphylococcus aureus (MRSA) stains have been reported.^46,47 Several geranylated flavonoids from methanolic extract of P. tomentosa fruits show remarkable inhibitory activity against SARS viral protease because of an unusual 3, 4-dihydro-2H-pyran motif, which targets the cysteine residues on the RNA virus’s replicase protein: the papain-like protease⁴⁸. Furthermore, anti-microbial efficacy and synergistic action with conventional antibiotics of six geranylated flavonoids extracted from P. tomentosa fruits have been found.⁴⁹ Mimulone, a C-geranyl flavonoid derived from the fruits of P. tomentosa, has been demonstrated to activate autophagy in human lung cancer cell lines via p53-mediated control of AMPK/mTOR signalling, resulting in tumour cell apoptosis.⁵⁰ The fruits of P. tomentosa (misidentified as P. coreana) were reported to contain eleostearic acid, flavonoids, fatty oil, and alkaloids.⁵¹

Campneoside-I identified from the species Paulownia inhibits Staphylococcus aureus, S. pyogenes, and S. faecium.⁵¹ Eight C-6geranylflavonoids were extracted from an ethanol extract of P. tomentosa fruits and their antibacterial and yeast inhibitory properties were reported.⁵² According to experimental research on the pharmacological activity of paulownin, the molecule provides considerable health advantages such as antiinflammatory and analgesic effects, increasing immunity, and reducing blood glucose; and has little toxicity.⁵³

Paulownia elongate is a medicinal plant that contains some bioactive ingredients. The roots of paulownia elongate was used in this research to investigate the phytochemical profile of its methanol extracts and the antibacterial activity of the extract on some bacterial organisms. The study found a large number of organic compounds in the roots of Paulownia elongata, and these chemicals account for a large portion of the plant's claimed and documented ethno medicinal and bioactive potential. The methanol aqueous extracts of paulownia elongata roots when displayed on the chromatogram showed the different retention time, peak area and height as it accounts for certain compounds. The highest compound identified was theobromine (34.42%), oleic acid (37.87%), followed by oxime, methoxy-phenyl (3.32%) and methyl stearate (4%). The least compounds identified were ethanol, 2-(hexyloxy) and alpha-pineme (1.19%).

The results of phytochemical screening revealed the extract's potential, which led to its antibacterial activities as reported in this study. When compared to the test controls, the anti-bacterial activity generated a substantial reduction in growth rate against the tested species of microorganisms at 30g provided concentration. Salmonella typhi and Escherichia coli likewise demonstrated substantial activity (p<0.05) at 30g when compared to the scontrol. More research is needed to assess the prospective effectiveness of the crude extracts of paulownia elongate as antimicrobial, antimalarial and anticancer agents. And, more research aimed at isolating and elucidating the structure of antibacterial active constituents from the plant, is well recommended.

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1. Arowora K, Ugwuoke K, Abah M, et al. Evaluation of Serum biochemical parameters in male wistar rats administered with Azadirachta Indica silver nanoparticles. Asian Journal of Science, Technology, Engineering, and Art. 2024;2(3):462–475.
2. Marshall N A, Friedel M, van Klinken RD, et al. Considering the social dimension of invasive species: the case of buffel grass. Environ Sci Policy. 2011;14:327–338.
3. Hao DC. Genomics and evolution of medicinal plants. Ranunculales Medicinal Plants. 2019:1–33.
4. Ekele JU. Phytochemical analysis of six anti-venom medicinal plants. Journal of Medicinal Plants Studies. 2023;11(3):71–79.
5. Zhu ZH, Chao CJ, Lu XY, et al. Paulownia in China: Cultivation and utilization. Chinese Acad for Asian Network for Biol Sci. 1986.
6. Joshee, N. Paulownia: A multipurpose tree for rapid lignocellulosic biomass production. In: Kole C, Joshi CP, Shonnard D, editors. Hand of Bioenerg Crop Plants. Taylor & Francis. 2012.
7. Li P, Oda J. Flame retardancy of Paulownia wood and its mechanism. J Mater Sci. 2007;42(20):8544–8550.
8. Basu C, Joshee N, Gazelian T, et al. Crossspecies PCR and field studies on Paulownia elongata: A potential bioenergy crop. 2015;2:12–23.
9. Vaughan SF, Dan Dinelli F, Tisserat B, et al. Creeping bentgrass growth in sand-based root zones with or without biochar. Sci Hort. 2015;197:592–96.
10. Jiangsu New Medical College. Chin Med Dict Shanghai People’s Publishing House; Shanghai. 1977.
11. Jiang JP. Plantation of Chinese Forestry Press, Beijing. 2003.
12. Zhao LZ. Clinical applications of Mag Tradit Chin Ext Med. 2003;12(2):48.
13. Šmejkal K, Grycová L, Marek R, et al. C-Geranyl compounds from Paulownia tomentosa J Nat Prod. 2007;70(8):1244–1248.
14. Kang, K. H., Huh, H., Kim, B. K. and Lee, C. K. An antiviral furanoquinone from Paulownia tomentosa Phytother Res. 1999; 13(7):624–626.
15. Guo JH, Du G, Shen LL. The research progress of the chemical compositions and pharmacological actions of Paulownia flowers. Herald Med. 2011;30(2):234–235.
16. Luo JH, Li K, Entomack B. Research progress on Paulownia fortune. Guizhou Agri Sci. 2010;38(1):200–202.
17. Martins AL, Silas TV, Abah MA, et al. Isolation, identification, andcharacterization of heavy metal-resistant bacteria from soil samples collected at a cement company in Nigeria. Asian J Trop Biotechnol. 2024;21:26–32.
18. Cao YC, Shao CJ, He Y. The overview of the chemical compositions and biological activities of the genus Chin J Med. 2008;8(4):308–310.
19. Radev R, Sokolova K, Tsokeva Z, et al. Antioxidant activity on total extract of Haberlea rhodopensis. VI National Congress of Pharm. 2009.
20. Radev R. Pharmacological effects of phenylethanoid glycosides. J Clin Med. 2010;3(2):20–23.
21. Carey FA. Organic chemistry. 7^th McGraw-Hill Companies; USA. 2007.
22. Dixon RA, Dey PM, Lamb CJ. Phytoalexins: enzymology and molecular biology. Adv Enzymol Relat Areas Mol Biol. 1983;55:1–136.
23. Mahomoodally MF, Gurib-Fakim A, Subratty, AH. Antimicrobial activities and phytochemical profiles of endemic medicinal plants of Mauritius. Pharm Bio. 2005;43(3):237–242.
24. Pandey AK. Anti-staphylococcal activity of a pan-tropical aggressive and obnoxious weed Parihenium histerophorus: An in vitro Nat Acad Sci Letters. 2007;30(11-12):383–386.
25. Agrawal AD. Pharmacological activities of flavonoids: A review. J Pharm Sci Nanotech. 2011;4(2):1394–1398.
26. Kollár P, Bárta T, Závalova V, et al. Geranylated flavanone mentodiplacone B inhibits proliferation of human monocytic leukaemia (THP-1) cells. Brit J Pharmacol. 2011;162:1534–1541.
27. Kang KH, Jang SK, Kim BK, et al. Antibacterial phenylpropanoid glycosides from Paulownia tomentosa Arch Pharm Res. 1994;17(6):470-475.
28. Gerritsen ME, Carley WW, Ranges GE, et al. Flavonoids inhibit cytokine-induced endothelial cell adhesion protein gene expression. Am J Pathol. 1995;147(2):278292.
29. Capasso A, Pinto A, Sorrentino R, et al. Inhibitory effects of quercetin and other flavonoids on electrically induced contractions of guinea pig isolated ileum. J Ethnopharmacol. 1991;34(2-3):279–281.
30. Ko HH, Weng JR, Tsao LT, et al. Anti-inflammatory flavonoids and pterocarpanoid from Crotalaria pallida and assamica. Bioorg. Med Chem Lett. 2004;14(4):1011–1014.
31. Zhang YH, Park YS, Kim TJ, et al. Endothelium-dependent vasorelaxant and antiproliferative effects of apigenin. Gen Pharmacol., 2000;35(6):341–347.
32. Cos P, Ying L, Calomme M, et al. Structure-activity relationship and classification of flavonoids as inhibitors of xanthine oxidase and superoxide scavengers. J Nat Prod. 1998;61(1):71–76.
33. Czyz J, Madeja Z, Irmer U, et al. Flavonoid apigenin inhibits motility and invasiveness of carcinoma cells in vitro. Intl J Cancer. 2005;114(1):12–18.
34. Parajuli P, Joshee N, Rimando AM, et al. In vitro anti-tumor mechanisms of various Scutellaria extracts and their constituent flavonoids. Planta Medica. 2009;75(1):41–48.
35. Zima A, Hosek J, Treml J. Antiradical and cytoprotective activities of several C-geranyl substituted flavanones from Paulownia tomentosa Molecules. 2010;15(9):6035–6049.
36. Popova TP, Baykov BD. Antimicrobial activity of aqueous extracts of leaves and silage from Paulownia elongata. Am J Biol Chem Pharm Sci. 2013;1(2):8–15.
37. Jung S, Moon HI, Ohk J, et al. Inhibitory effect and mechanism on antiproliferation of Isoatriplicolide Tiglate (PCAC) from Paulownia coreana. 2012;17:59455951.
38. Ayo VI, Adondua MA, Morayo AE, et al. Effect of Lactuca sativa supplemented diet on Poloxamer 407 inducedhyperlipidemic albino rats (Rattus norvegicus). Asian J Nat Prod Biochem 2023;21:67–78.
39. Varlyakov I, Radev V, Slavov T, et al. Blood parameters in yearling sheep fed Paulownia (Paulownia spp.) leaves. Agric Sci Tech. 2013;5(4):405–409.
40. Wei XY, He Y, Jiang In vitro antibacterial activity of Paulownia flowers and the measurement of flavonoid content. Res Dev Nat Prod. 2006;18(3):401–404.
41. Ji P, Chen C, Hu Y, et al. Antiviral activity of Paulownia tomentosa against enterovirus 71 of hand, foot, and mouth disease. Biol Pharm Bull. 2015;38(1):1–6.
42. Ibrahim HA, El-Hawary SS, Mohammed MMD, et al. Chemical composition, antimicrobial activity of the essential oil of the flowers of Paulownia tomentosa (Thunb.) Steud. Growing in Egypt. J Appl Sci Res. 2013;9(4):3228–3232.
43. Si CL, Liu SC, Hu HY, et al Activity guided screening of the antioxidants from Paulownia tomentosa tomentosa bark. Biores. 2013;8(1):628–637.
44. Cho JK, Ryu YB, Curtis-Long MJ, et al. Cholinestrase inhibitory effects of geranylated flavonoids from Paulownia tomentosa Bioorg Med Chem. 2012;20(8):2595–2602.
45. Navrátilová A, Schneiderová K, Veselá D, et al. Minor C-Geranylated flavanones from Paulownia tomentosa fruits with MRSA antibacterial activity. Phytochem. 2013;89:104–113.
46. Navrátilová A, Nešuta O, Vančatová I, et al. C-Geranylated flavonoids from Paulownia tomentosa fruits with antimicrobial potential and synergistic activity with antibiotics. Pharma Biol. 2016;54(8):1398–1407.
47. An HK, Kim KS, Lee JW, et al. Mimulone-induced autophagy through p53mediated AMPK/mTOR pathway increases caspase-mediated apoptotic cell death in A549 human lung cancer cells. PLoS One. 2014;9(12):e114607.
48. Kim JK, Lee YS, Kim SH, et al. Inhibition of aldose reductase by phenylethanoid glycoside isolated from the seeds of Paulownia Biol Pharm Bull. 2011;34(1):160–163.
49. Kazi M, Simabayasi T. A glycoside from Paulownia. Japan. 1932;93:27.
50. Li YJ, Zhong ZX, Zhou GF. The experimental research on the pharmacological effects of paulownin. The Guangxi Sci. 2007;14(4):405–406.
51. Ayo VI, Abah MA, Ekele JU, et al. Effects of Methanol Leaf Extract of Mucuna Pruriens on Male Anaemic Wister Rats, International Journal of Pharmacy and Pharmaceutical Studies. 2023;7(4):1–13.
52. Yakubu OE, Nwodo OFC, et al. In vitro determination of antioxidantactivities of the fractions obtained from Adansonia digitata L.(baobab) stem bark ethanolic extract using differentparameters. Curr Trend Biomed Eng Biosci. 2019;17(5):555973.
53. Ayo VI, Abah MA, Ale ME, et al. Phytochemical screening andproximate composition of methanol leaf extract of Phyllanthus niruri. Intl J Med All Body Res. 2023a;4(2):1–5.
54. Šmejkal K, Stanislav C, Kloucek P. Antibacterial C-geranyl flavonoids from Paulownia tomentosa J Nat Prod., 2008(b);71(4):706–709.
55. Asai T, Tanno Y. Highly schizotypal students have a weaker sense of self-agency. Psychiatry Clin Neurosci. 2008 Feb;62(1):115-119.
56. Šmejkal K, Babula P, Slapetová T, et al. Cytotoxic activity of C-geranyl compounds from Paulownia tomentosa Plant Med., 2008a;74(12):1488–1491.
57. Ayan S, Gercek V, Sahin A. Performance of nursery stage of Paulownia Sieb. & Zucc. Species and origins. Rev Fac for Uni of SuleymanDemirel. 2002;2:41–56.
58. Angelova-Romova A, Koleva MA, Antova Get al. Lipid composition of Paulownia seeds grown in Bulgaria. Trakya Uni J Sci. 2011;13(2):101–111.