A study of the seasonal variation in the antimicrobial constituents of the leaves of Loranthus micranthus sourced from Percia americana

A comparative study of the antimicrobial constituents of the leaves of Loranthus micranthus (parasitic on Percia americana) harvested at different seasons of the year, namely, January, April, July and November, was carried out. The air-dried and pulverized leaves harvested at the stated periods were extracted with petroleum ether and the extracts subjected to antimicrobial screening and phytochemical investigation. Using various solvent treatments the powdered leaves harvested in April were fractionated into four fractions, A, B, C and D; each fraction was screened for antimicrobial activity and phytochemical constituents. Phytochemical analysis of the extracts showed the presence of tannins, flavonoids, alkaloids, terpenoids and saponins with some of these constituents showing variations across the seasons. Broad spectrum antibacterial activity was observed for all the extracts. However, the activity against Bacillus subtilis and Salmonella typhi was significantly (p<0.001) lower for the extracts of the leaves harvested in January when compared with the extracts of the leaves harvested in the other months. Only the extracts of the leaves harvested in April showed antifungal activity. Fractions A, B and D showed antimicrobial activity comparable (p<0.05) to standard antibiotic, chloramphenicol. These fractions are rich in tannins (A and D), alkaloids (A) and terpenoids (B). The presence of alkaloids only in April and July may explain the higher antimicrobial activity observed in these months. Earlier reports showed that alkaloids may be responsible for the antimicrobial activity [1]. In conclusion, mistletoe used as a herbal remedy for nonspecific infections may be preferentially harvested in April and July.

Acknowledgments: The authors are grateful to Mr. Ozioko of Bio-resource Development and Conservation Centre Nsukka, Enugu State, Nigeria for authenticating the plant material.

References: [1] Osadebe PO and Ukwueze SE. (2004). J of Bio. Res. and Biotechn. 2: 18–23.