Screening for alternative antibiotics: an investigation into the antimicrobial activities of medicinal food plants of Mauritius.

The present study was designed to evaluate the antimicrobial activities of 2 endemic medicinal plants; Faujasiopsis flexuosa (Asteraceae) (FF) and Pittosporum senacia (Pittosporaceae) (PS) and 2 exotic medicinal plants, Momordica charantia (Cucurbitaceae) (MC) and Ocimum tenuiflorum (Lamiaceae) (OT) that forms part of local pharmacopoeia of Mauritius and correlate any observed activity with its phytochemical profile. Aqueous and organic fractions of the leaves, fruits, and seeds of these plants were subjected to antimicrobial testing by the disc diffusion method against 8 clinical isolates of bacteria and 2 strains of fungus. It was found that MC, OT, and FF possessed antimicrobial properties against the test organisms. The MIC for MC ranged from 0.5 to 9 mg/mL and that of FF from 2 to 10 mg/mL and the lowest MIC value (0.5 mg/mL) was recorded for the unripe fruits of MC against E. coli. On the other hand, higher concentration of the unripe MC fruit extract of 9 mg/mL was needed to be effective against a resistant strain of Staphylococcus aureus (MRSA). The antimicrobial effect against MRSA was lost upon ripening of the fruits. The methanolic extract of both MC and FF showed highest MIC values compared to the corresponding aqueous extract, which indicates the low efficacy and the need of higher doses of the plant extract. Phytochemical screening of the plants showed the presence of at least tannins, phenols, flavonoids, and alkaloids, which are known antimicrobial phyto-compounds. In conclusion, the observed antimicrobial properties would tend to further validate the medicinal properties of these commonly used endemic medicinal and food plants of Mauritius.