Does seasonal variation influence the phytochemical and antibacterial properties of Carpobrotus edulis?

Carpobrotus edulis L. (family Aizoaceae) has been used by locals over the years to treat microbial infections. Extracts of varying polarities were prepared from the leaf debris and filtrate of a spring and an autumn harvest of C. edulis. Thin layer chromatography was used to analyze the phytocompounds of the extracts as well as to assay the plant for antioxidant compounds. The spring harvest showed equal distribution of the phytochemicals within the leaf debris and the filtrate, but there was a high prevalence of phytocompounds within the leaf debris extracts of the autumn sample. An antioxidant compound was intensely pronounced in the autumn extracts of intermediate polarity and in the polar extract. The plant was evaluated for antibacterial activity against Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Staphylococcus aureus by using a two-fold serial microdilution method as well as bioautography. The spring extracts were more potent against all test organisms, having MIC values that were lower than the autumn extracts. When taking the total activity of each extract into account, the autumn extracts showed higher efficacy than the extracts from the spring sample. The antibacterial activity observed in the extracts of both seasons somewhat validated the ethnomedicinal use of C. edulis