Antimicrobial Activity of 23 Endemic Plants in Madagascar

Purpose: To screen the crude methanol extracts obtained from 23 endemic plants in Madagascar for antimicrobial activity. Methods: In order to assess the antimicrobial properties of the extracts; their minimum inhibitory concentrations (MICs) were obtained using the broth microdilution method. The six test pathogenic species used were Bacillus subtilis; Staphylococcus aureus; Escherichia coli; Salmonella typhi; Pseudomonas aeruginosa and Candida albicans. Bioautography agar overlay test and phytochemical screening were also performed on the most active extracts. Results: From the 23 plants tested; 16 of which are used in traditional medicine; Poivrea phaneropetala Combretaceae); Koehneria madagascariensis (Lythraceae) and Rhopalopilia perrieri (Opiliaceae) exhibited the broad spectrum of activity; being active against all the test organisms; while Monoporus clusiifolius (Myrsinaceae) showed the strongest antifungal activity against Candida albicans with a minimal inhibitory concentration of 0.250 mg/ml. Bioautography and phytochemical analysis of the five active extracts against bacterial strains and of one active extract against C. albicans indicate that the active compounds responsible for antimicrobial activity may be mainly flavonoids and/or terpenes. Conclusion: These preliminary results are the first antimicrobial studies on these of some of them in traditional medicine

Endophytic fungi from leaves of Centella asiatica: occurrence and potential interactions within leaves.

Fungal endophytes were isolated from leaves of Centella asiatica (Apiaceae) collected at Mangoro (middle eastern region of Madagascar, 200 km from Antananarivo). Forty- five different taxa were recovered. The overall foliar colonization rate was 78%. The most common endophytes were the non-sporulating species 1 (isolation frequency IF 19.2%) followed by Colletotrichum sp.1 (IF 13.2%), Guignardia sp. (IF 8.5%), Glomerella sp. (IF 7.7%), an unidentified ascomycete (IF 7.2%), the non-sporulating species 2 (IF 3.7%) and Phialophora sp. (IF 3.5%). Using sequences of the ribosomal DNA internal transcribed spacer (ITS) regions, major endophytes (IF > 7%) were identified as xylariaceous taxa or as Colletotrichum higginsianum, Guignardia mangiferae and Glomerella cingulata. Results from in vitro fungal disk experiments showed a strong inhibitory activity of the xylariaceous non-sporulating species 1 against G. mangiferae and C. higginsianum and of C. higginsianum against G. mangiferae. This can be explained by antagonism between dominant taxa.