Antimicrobial investigation of Tephrosia Vogelii hook.f from Hai District in Tanzania towards development of antifungal agents for topical application

Abstract

Infectious diseases such as fungal diseases are the global health problem. Moreover, antimicrobial resistance to modern fungicides and antibiotics is even perplexing in the health settings. Such situation needs serious attention to search for alternative antimicrobial agents. Thus, this study aimed to investigate antimicrobial activity of Tephrosia vogelii Hook.f found in Tanzania and develop antifungal agents therefrom. The n-hexane, dichloromethane and methanolic extracts from leaves and roots of Tephrosia vogelii were evaluated for antimicrobial activity against Candida albicans (ATCC 90028), Cryptococcus neoformans (clinical isolate), Staphylococcus aureus (ATCC25923), Escherichia coli (ATCC29953), Klebsiella pneumoniae (ATCC 700603) and Salmonella typhi (NCTC 8385). A serial dilution method using the sterilized 96 wells of polystyrene microliter plates were used to determine the minimum inhibitory concentrations (MIC) of extracts. The in vivo toxicity of methanolic leaf and root extracts was evaluated using albino rats. Extracts doses of 600, 1200, 2000 and 5000 mg/kg body weight were evaluated for lethality test while doses of 600, 1200 and 2000 mg/kg body weight subjected for sub-acute toxicity test. Gas Chromatography-Mass Spectrometry (GC-MS) technique was employed to appraise phytochemical compounds present. Antifungal agent for topical application was formulated and evaluated through in vitro and in vivo test to establish its effectiveness. The study results revealed that n-hexane and dichloromethane extracts exhibited the lowest activity. Equally, methanolic root and leaf extracts exhibited high activity at MICs ranging from 0.625 - 5.0 mg/mL against assayed pathogens. Phytochemical screening of both methanolic leaf and root extracts revealed the presence of tannins, flavonoids, terpenes, fatty acids and saponins. The GC-MS analysis unveiled the presence of ten phytocompounds. Five compounds; demethylmunduserone sumatrol, munduserone, hexadecanoic acid and hexadecanoic acid, methyl ester are new and this is the first time to be reported from Tephrosia vogelii. Furthermore, toxicity evaluation revealed that methanolic leaf and root extracts of Tephrosia vogelii were not deleterious at highest dose of 5000 mg/kg body weight. Though there was no mortality recorded, histopathological examination revealed toxicity indices due to vacuolation and necrosis in hepatocytes under treatment of methanolic root extracts of dose 2000 mg/kg body weight. The herbal cream prototype (CBTV3) was formulated, and it exhibited antimicrobial activity through in vitro and in vivo tests. The development of herbal cream prototype from Tephrosia vogelii Hook.f is hereby reported for the first time.