Phytoconstituents and Antimycobacterial Activities of Root Extracts and Fractions from Vernonia glabra, (Steetz) Vatke

Abstract

Vernonia glabra is used by Malawian traditional healers to treat a myriad of ailments including shingles, diabetes, dysentery, diarrhoea, cough, wounds, gonorrhoea, and gastrointestinal problems. This study evaluated phytoconstituents and the in vitro antimycobacterial activities of the crude extracts and fractions from roots of Vernonia glabra. Agar disk diffusion and modified broth microdilution assays were used to determine the antimycobacterial activities of dichloromethane (DCM) and ethyl acetate (EtOAc) crude extracts and fractions from the roots. Gas chromatography-mass spectrometry (GC-MS) and Fourier-transform infrared spectroscopy (FTIR) analyses were used to characterise the major compounds in the crude extracts and fractions. The EtOAc fraction exhibited the highest antimycobacterial activity against Mycobacterium tuberculosis H37Rv. The EtOAc fraction achieved a minimum inhibitory concentration (MIC) of 4.88 μg/mL and a half-maximal inhibitory concentration (IC50) value of 38.37 μg/mL, whereas gentamycin, a standard drug, achieved MIC and IC50 values of 3.13 μg/mL and 3.88 μg/mL, respectively. GC-MS and FTIR analyses of the EtOAc fractions revealed the presence of hexadecenoic acid, methyl ester (0.39%), diisooctyl phthalate (24.56%), oxalic acid, allyl undecyl ester (4.66%), bis(2-ethylhexylphthalate) (5.41%), octacosane (51.12%), tetradecane (12.63%), phenol, 3,5-bis(1,1-dimethylethyl) (0.07%), and 2-hydroxy-4-methylbenzaldehyde (6.47%). The identified compounds are reported in the literature to possess antimicrobial and anticancer activities. It was evident from the comparison of the hill slope (HS) values of the dose-response curves of the fraction (−1.005) and its crude extract (−1.322) that repeated fractionation improved the activity. Therefore, this study showed that the roots of Vernonia glabra present a potential source of new leads for antimycobacterial drugs.

Exploring Antibacterial Properties of Bioactive Compounds Isolated from Streptomyces sp. in Bamboo Rhizosphere Soil

“…The ethyl acetate fraction of BS-16 was further characterized by FT-IR and GC–MS analysis. Through FT-IR, it was found that the phthalate compounds 1,2-benzenedicarboxylic acid, diisooctyl ester, phthalic anhydride, phthalic acid, and monoethyl ester were reported for antimicrobial activity . The closely related compound called dimethyl phthalate was found to deform the cell membrane and disrupt the membrane channels to induce antimicrobial activity .…”

“…Through FT-IR, it was found that the phthalate compounds 1,2-benzenedicarboxylic acid, diisooctyl ester, phthalic anhydride, phthalic acid, and monoethyl ester were reported for antimicrobial activity. 42 The closely related compound called dimethyl phthalate was found to deform the cell membrane and disrupt the membrane channels to induce antimicrobial activity. 43 Similarly, the presence of these compounds in the BS-16 ethyl acetate extract could have disrupted the bacterial cell membrane.…”

Ratanjot (<em>Alkanna tinctoria</em> L.) Root Extract, Rich in Antioxidants, Exhibits Strong Antimicrobial Activity Against Foodborne Pathogens and Is a Potential Food Preservative

“…DIOP from marine brown algae Sargassum wightii was found to be an antimicrobial compound [62]. Similarly, DIOP was also identified as a phytochemical in Vernonia glabra root ethyl acetate extracts, which showed antitubercular activity against Mycobacterium tuberculosis [63].…”