Abstract
Humboldtia unijuga is a rare tree species native to the Western Ghats and has been traditionally used for treating various ailments. Despite its medicinal importance, scientific studies on this plant remain limited. The present research was undertaken to examine the phytochemical composition, antibacterial activity, and anti-diabetic potential of H. unijuga leaf extracts under laboratory conditions. Leaves were extracted successively using hexane, ethyl acetate, and methanol to obtain fractions with different polarities. Preliminary phytochemical screening revealed the presence of biologically important compounds such as alkaloids, flavonoids, tannins, phenolics, saponins, and terpenoids in all extracts. Among them, the methanolic extract showed the highest concentration of phenolic and flavonoid compounds. Antibacterial activity was evaluated against selected Gram-positive and Gram-negative bacteria using the agar well diffusion method. All extracts exhibited concentration-dependent inhibitory effects, with the ethyl acetate extract showing the most pronounced and broad-spectrum activity, particularly against Staphylococcus aureus. The anti-diabetic potential of the extracts was assessed through α-amylase and α-glucosidase inhibition assays. The methanolic extract demonstrated strong inhibitory activity against both enzymes, with IC₅₀ values comparable to the standard drug acarbose. A positive correlation was observed between phenolic content and biological activity, indicating the major role of phenolic compounds in mediating these effects. Overall, this study provides scientific evidence supporting the traditional use of H. unijuga and highlights its potential as a natural source of bioactive compounds for managing bacterial infections and type 2 diabetes. Further studies are required to isolate active constituents and validate these findings through in vivo experiments.
Keywords: Humboldtia unijuga, antibacterial activity, anti-diabetic potential, type 2 diabetes mellitus.
Nair, R. V. R., Jayasree, D. V., Biju, P. G., & Baby, S. (2019). Anti-inflammatory and anticancer activities of erythrodiol-3-acetate and 2,4-di-tert-butylphenol isolated from Humboldtia unijuga. Natural Product Research, 33(15), 2251–2255.
https://doi.org/10.1080/14786419.2018.1531406
Sujana, K. A., & Nagaraju, S. (2021). Humboldtia Vahl (Fabaceae): A review on ethnobotany, phytochemistry and pharmacology. Phytomedicine Plus, 1(4), 100080. https://doi.org/10.1016/j.phyplu.2021.100080
Bauer, A. W., Kirby, W. M. M., Sherris, J. C., & Turck, M. (1966). Antibiotic susceptibility testing by a standardized single disk method. American Journal of Clinical Pathology, 45(4), 493–496.
Bernfeld, P. (1955). Amylases, α and β. In S. P. Colowick & N. O. Kaplan (Eds.), Methods in enzymology (Vol. 1, pp. 149–158). Academic Press.
Brand-Williams, W., Cuvelier, M. E., & Berset, C. (1995). Use of a free radical method to evaluate antioxidant activity. LWT - Food Science and Technology, 28(1), 25–30.
Chang, C.-C., Yang, M.-H., Wen, H.-M., & Chern, J.-C. (2002). Estimation of total flavonoid content in propolis by two complementary colorimetric methods. Journal of Food and Drug Analysis, 10(3), 178–182. https://doi.org/10.38212/2224-6614.2748
Cosam, J. W., Kusari, S., & Spiteller, M. (2009). In vitro α-amylase and α-glucosidase inhibitory effects of some medicinal plants used in diabetes mellitus management. Journal of Medicinal Plants Research, 3(12), 1023–1029.
Cowan, M. M. (1999). Plant products as antimicrobial agents. Clinical Microbiology Reviews, 12(4), 564–582.
Ekor, M. (2014). The growing use of herbal medicines: Issues relating to adverse reactions and challenges in monitoring safety. Frontiers in Pharmacology, 4, 177. https://doi.org/10.3389/fphar.2013.00177
Eom, S. H., et al. (2011). Antibacterial activities of plant extracts by agar well diffusion method. Journal of Microbiology and Biotechnology, 21(5), 501–507.
Harborne, J. B. (1998). Phytochemical methods: A guide to modern techniques of plant analysis (3rd ed.). Chapman & Hall.
Kuete, V. (2010). Potential of Cameroonian plants and derived products against microbial infections: A review. Planta Medica, 76(14), 1479–1491. https://doi.org/10.1055/s-0030-1250027
Kumar, S., Narwal, S., Kumar, V., & Prakash, O. (2011). α-Glucosidase inhibitors from plants: A natural approach to treat diabetes. Pharmacognosy Reviews, 5(9), 19–29. https://doi.org/10.4103/0973-7847.79096
Miller, G. L. (1959). Use of dinitrosalicylic acid reagent for determination of reducing sugar.
Nair, R. V. R., et al. (2023). Antiproliferative activity of secondary metabolites isolated from Humboldtia unijuga Bedd. Medicinal Chemistry Research, 32(5), 1023–1034. https://doi.org/10.1007/s00044-023-03064-4
Singleton, V. L., & Rossi, J. A. (1965). Colorimetry of total phenolics with phosphomolybdic-phosphotungstic acid reagents. American Journal of Enology and Viticulture, 16(3), 144–158.
Singleton, V. L., Orthofer, R., & Lamuela-Raventós, R. M. (1999). Analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. In L. Packer (Ed.), Methods in enzymology (Vol. 299, pp. 152–178). Academic Press. https://doi.org/10.1016/S0076-6879(99)99017-1
Sreekumari, et al. (2025). An assessment of the ethnomedicinal properties of endemic flowering plants of the Western Ghats, India. Pharmacognosy Reviews, 19(38), 260–282.
Surendran, S., Prabha, A. C., Ramasubbu, R., & Krishnaraj, M. V. (2021). Humboldtia Vahl (Fabaceae): A review on ethnobotany, phytochemistry and pharmacology. Phytomedicine Plus, 1(4), 100080.
https://doi.org/10.1016/j.phyplu.2021.100080
Trease, G. E., & Evans, W. C. (2009). Pharmacognosy (16th ed.). Saunders Elsevier.
Valgas, C., Machado de Souza, S., Smânia, E. F. A., & Smânia, A. Jr. (2007). Screening methods to determine antibacterial activity of natural products. Brazilian Journal of Microbiology, 38(2), 369–380.
https://doi.org/10.1590/S1517-83822007000200034
World Health Organization. (2000). General guidelines for methodologies on research and evaluation of traditional medicine. WHO.