Antibiotic activity of pteridophytes

The occurrence of antibiotic activity in the extracts of 114 species of pteridophytes (27 families, 61 genera) has been surveyed. The plants were extracted in water, methanol, 70% ethanol, acetone and ether and assayed against 3 gram-positive, I acid-fast and 5 gram-negative bacteria and 3 fungal plant pathogens. Sixty-seven ferns and 6 fern allies, representing 64% of the samples examined, were antibiotic ally active. The active substances were in most cases antibacterial and only 3 possessed antifungal activity. Thirty-three species were inhibitory to gram-positive bacteria alone, 9 exclusively against gram-negative bacteria and 15 to both. Twenty species were inhibitory to penicillin-resistant Staphylococcus aureus, 16 against Mycobacterium phlei, 24 against Salmonella typhi, 16 against Vibrio cholerae and 3 against Pseudomonas aeruginosa. Only Dryopteris coch-leata was active against both bacteria and fungi. Five other species of Dryopteris showed remarkable antibacterial activity. The ferns of “Adiantum group” were found to be particularly active against gram-positive bacteria. The polypodiaceous ferns constitute a rich group of which Microsorium alternifolium, Leptochillus decurrens, Polypodium irioides, Pyrrosia mannii and Phymatodes ebenipes deserve special mention. Several thelypteroid, davalloid and athyroid ferns were also fairly active.