The volatile constituents from Lepidium sativum and Tridax procumbens shoots exhibit antimicrobial effect and inhibitory activities against α-amylase enzyme and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical

Abstract

The bioprospecting of wild functional food plants used in the urban communities in developing countries as sources of food and medicine has been on the rise steadily. Lepidium sativum and Tridax procumbens are wild edible plants in Nigeria with tremendous ethnomedicinal uses. In this research, volatile extracts were obtained from the shoots of the two plants via steam distillation and subjected to Gas Chromatography Mass Spectrometry analysis, antimicrobial analysis and inhibitory activities against α-amylase enzyme and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, respectively. A white color volatile extract was obtained from L. sativum shoot while a translucent volatile extract with sweet scent was obtained from T. procumbens shoot. Both extracts consist of vary constituents of phytochemicals. The extract from L. sativum only showed moderately susceptibility against Streptococcus pneumonea with zone of inhibition of 11.5 mm among the selected microbes while extract from T. procumbens showed a broader susceptibility towards more microbes with higher zone of inhibition values and a better inhibitory activity against Staphylococcus aureus with minimum inhibition concentration MIC of 31.23 mg/g. Both extracts have better alpha-amylase inhibitory activity with EC₅₀ values of 134.48 μg/mL (L. sativum) and 106.74 μg/mL (T. procumbens), respectively when compared to the EC₅₀ value of 165.93 μg/mL of the standard drug acarbose. However, the standard drug (ascorbic acid) exhibited better inhibitory activity against DPPH radical with EC₅₀ value of 41.69 μg/mL when compared to their EC₅₀ values of 47.71 and 48.63 μg/mL, respectively. The results show that the volatile extracts contain phytochemicals with antimicrobial, anti-diabetic and antioxidant potentials.