Antibacterial, antifungal, antioxidant, brine shrimp lethality and polyphenolic content of <i>Holarrhena</i> <i>mitis</i> (Vahl) R.Br. ex Roem. & Schult

Abstract

Holarrhena mitis (Vahl) R.Br. ex Roem. & Schult. which is an endemic plant growing mainly in the dry regions of the low-country has been used in the treatment of dysentery in Ayurvedic medicine. During the present study, we tested antibacterial, antifungal, antioxidant activities and brine shrimp lethality, as well as the total phenolic content of the dichloromethane, ethyl acetate and methanol extracts of the bark and leaves of H. mitis. The methanol extract of bark produced a measurable zone of inhibition against two Candida species, namely Candida albicans, Candida krusei among all five tested species and against both dermatophytes, Microsporum gypseum and Tricophyton mentagrophytes. In addition, the methanol extract of bark showed very strong antifungal activity against C. krusei (20 mm), which is very close to that of the positive control ketoconazole (22 mm). Both dicholoromethane extracts of bark and leaves and methanol extracts of leaves showed an activity against both tested strains of Staphylococcus aureus but were negative against Escherichia coli and Salmonella enteritidis. However, the rest of the extracts exerted an active against all the tested bacterial strains. In the brine shrimp cytotoxicity assay, the dichloromethane extracts of both leaves and bark showed lower LC 50 values (27.13 ppm and 9.38 ppm, respectively) than that of positive control, K 2 Cr 2 O 7 , (35.74 ppm) indicating cell toxicity. Compared to the positive control, DL-α-tocopherol (IC 50 : 12.2 ppm), the antioxidant activity of the ethyl acetate and methanol extracts of leaves exhibited comparable activity (IC 50 :16.9 ppm and 29.8 ppm, respectively). Antioxidant activity correlated well with the polyphenol content of methanol and ethyl acetate extracts (473.25 and 138.74 mg (GAE) /g, respectively) of leaves, with respect to gallic acid. These empirical results revealed that methanol extract of bark of H. mitis showed strong antifungal activity as well as very low brine shrimp lethality indicating that it would be a potential nontoxic anti-fungal natural product. The dichloromethane extracts exhibited strong brine shrimp lethality and may contain potential natural anticancer lead compounds. Ethyl acetate extracts of both leaves and bark having significant antibacterial activity, would be source of potential antibacterial lead compounds.

Antifungal, antibacterial, and AChE inhibitory activity of the alkaloid mixture of <em>Holarrhena mitis</em> (Vahl) R.Br. ex Roem. & Schult (Kirimawara)

“…In our previous study, several bioactivities in different sequential extracts of bark and leaves of H. mitis such as significant antifungal activity against Candida sp. which was very close to that of the positive control ketoconazole, moderate antibacterial activity against Staphylococcus aureus (ATCC 29213) and moderate antioxidant activity were observed and have directed for further studies on isolation and identification of the corresponding active compounds (Wickramasingha et al, 2018).…”

“…Its bark is used in traditional medicine for the treatment of dysentery. The antibacterial, antifungal, antioxidant activities and brine shrimp lethality of sequential extracts of bark and leaf extracts of H. mitis were previously reported (Wickramasingha et al, 2018).…”