Antimicrobial, antioxidant and quantitative phytochemical evaluation of the dichloromethane and methanolic leaf extracts of Solenostemon monostychus P. Beauv

Abstract

Solenostemon monostachyus P. Beauv (Lamiaceae family) is an important herb that is widespread in West and Central Africa.The leaves are used in various decoctions traditionally to treat diseases most especially microbial infections associated with the foot. In this study, the phytochemicals (qualitative and quantitative) of the plant were determined. The antimicrobial and antioxidant activities of the plant were also evaluated by standard methods. Results showed alkaloids, tannins, flavonoids, saponins phenolics in the methanolic extract of Solenostemon monostachyus. Cardiac glycosides and steroids absent in the methanolic extract were found present in the dichloromethane extract. The quantitative phytochemicals recorded were alkaloids (18.05 ± 0.87%), saponins (11.3 ± 0.56 %), tannins (3.3 ± 0.19 GAE). The antioxidant activity testing showed that the methanolic extract has higher DPPH scavenging ability over dichloromethane extract and standard ascorbic acid. In the antimicrobial activity testing, the cup-plate diffusion method was used and the result showed that the dichloromethane extract inhibited the growth of Bacillus species at concentrations 100 mg/ml, 50 mg/ml, 20 mg/ml and 10 mg/ml while methanolic extract inhibited the growth of bacillus species only at 100 mg/ml with 5 mm zone of inhibition. However, both methanol and dichloromethane extract showed no antimicrobial activity on the other test organisms such as Psudomonas aeruginosa, Escherichia coli and Staphylococcus aureus. In conclusion both methanolic and dichloromethane extracts of Solenostemon monostachyus are potential sources of antimicrobial and antioxidant.