Comparative Analysis of the Phytochemicals, Minerals, Antioxidant and Antimicrobial Activities of Aqueous and Ethanolic Extracts of Rauvolfia vomtoria Leafs

Abstract

In this study, the phytochemicals, B vitamins, minerals, antioxidants and antimicrobial activities of aqueous and ethanolic extracts of Rauvolfia vomtoria leaves were determined and compared. Qualitative and quantitative phytochemical analysis, mineral and B vitamin composition, in vitro antioxidant capacity and antimicrobial properties of both extracts were determined using standard protocols.  Precise analysis of R. vomtoria revealed that the moisture content of the leaves was 8.90%, ash content was 7.70% and crude fiber content was 20.00%. The carbohydrate content of the leaves was 41%, crude protein content was 17. 00% and total fat content was 5.28%. Cardiac glycosides, tannins, phenols, saponins, phytates, steroids, terpenoids and alkaloids were detected in both aqueous and ethanolic extracts. However, significantly higher concentrations of saponins, tannins, flavonoids, steroids, alkaloids, cardiac glycosides and phytates were detected in the ethanolic extract compared to the aqueous extract. There was no significant difference in the amount of phenols and terpenoids in the two extracts (p>0.05). The thiamine content in the aqueous extract was 0.20 whereas that in the ethanolic extract was 0.27. The riboflavin content was higher in the ethanolic extract (1.80) than in the aqueous extract (1.40). Similarly, the niacin content of the ethanolic extract was 0.81 whereas that of the aqueous extract was 0.81. There was no significant difference in the calcium, magnesium and phosphorus values recorded for the two extracts (p>0.05). In contrast, there was a significant difference in the sodium, potassium, zinc, iron and copper contents of the two extracts with the aqueous extract containing higher amounts of potassium and zinc. The aqueous and ethanolic extracts had zones of inhibition against Enterobacter faecalis, Klebsiella pneumoniae, Salmonella typhi, Cetrobacter freundii and Shigella flexlerii. However, the zone of inhibition of the ethanolic extract against the tested organisms was higher than that of the aqueous extract. At a concentration of 10%, the aqueous and ethanolic extracts showed 87.29% and 92.03% DPPH scavenging activity, respectively. The percentage of inhibitory activity of the extracts against DPPH radical increased in a dose-dependent manner, with the ethanolic extract showing the highest DPPH radical inhibitory activity at a concentration of 50%. The results confirm that ethanol is a suitable solvent for the extraction of biologically active molecules from R.vomtoria leaves.