Phytochemical and antimycobacterial analysis of aqueous and ethanolic extracts of Annona muricata Linn (Soursop)

Abstract

Background: Against the backdrop evidenced in the threat Tuberculosis poses to developing economies, especially its prevalence among people in their productive (15-45) years; this preliminary study examined the phytochemical constituents and antimycobacterial effect of four (4) aqueous and ethanolic extracts from the fruit skin (epicarp) and leaf of Annona muricata Linn. Methods & Materials: Extracts were prepared with distilled water and 95% ethanol according to methods previously described. Phytochemical analysis of the extracts were carried out following standard protocols while the antimycobacterial activity was assayed by employing the Drug susceptibility testing (DST) procedure in a Biosafety Level 3 facility. Lowenstein Jensen (LJ) media were prepared with extracts at three concentrations (1, 40 and 250 μg/ml) following the project design and subsequently inoculated with 10-3 and 10-5 suspensions of both control (H37Rv) strain and a clinical isolate (MTB-584) of Mycobacterium tuberculosis. LJ media prepared with Rifampicin at 40 μg/ml was used as the standard drug for positive control while plain media with respective inoculum served as negative control. Four Ziehl-Neelsen's stain slides were also prepared to confirm the presence of organisms in the two suspensions employed for the two strains tested. Plain media inoculated with distilled water were employed as normal control to check for possible contaminant. The inoculated media and control slants were placed in an incubator at 37oC and observed every seven days for a period of 4 – 6 weeks. Subcultured strains of MTB on LJ slants Preparing LJ for DST Results: The phytochemical analysis collectively revealed the presence of tannins, saponins, flavonoids, anto- and betacyanins, terpenoids, phenols and steroids. The M. tuberculosis strains exhibited resistance to all the four extracts at tested concentrations as there was substantial growth with typical creamy non-pigmented morphology on all the LJ media prepared with extracts though with varied rate compared to the control. However, there was no growth on the media with standard drug and the media with distilled water as expected. Conclusion: It can therefore be inferred from the result that aqueous and ethanolic extracts from the fruit skin and leaf of A. muricata at tested concentrations have no antimycobaterial activity.