Economic maximization of alfalfa antimicrobial efficacy using stressful factors

Abstract

Objective: The present study addresses the effect of water deficit stress on the antimicrobial capacity of alfalfa (Medicago sativa) plants. Methods: Methanolic extracts of alfalfa plants grown in different soil types, varying in sand proportion, either alone or combined with various levels of water regimes were assessed for antibacterial and antifungal activities following cup plate method. The phytochemical profiles of plant extracts were also qualitatively screened using appropriate chemical reagents. Moreover, data were intensively processed via two different statistical designs. Results: Increasing sand amount induced the inhibitory effect of plant extracts on Escherichia coli, Klebsiella pneumonia, Proteus vulgaris, Salmonella typhi, Mucor circinelloides, Rhizopus azygosporus and R. microsporus with less pronounced action on Shigella flexneri, Staphylococcus epidermidis, Candida albicans and Emericella quadrillineata; as well as a reversed influence on Pseudomonas aerugenosa and Streptococcus pyrogenes. Furthermore, withholding irrigation water enhanced the plant suppressive action on E. coli, Salmonella typhi, Staphylococcus epidermidis, Candida albicans and R. microsporus with less marked or reversed influence on the other tested microbes. However, Pseudallescheria ellipsoidea, two species of Penicillium and five of Aspergillus could resist the studied plant extracts. The results also revealed that the extracts of water-unsatisfied plants generally contained higher amounts of alkaloids, amino acids, flavonoids, glycosides, phytosterols, saponins, steroids, tannins, terpenoids and reducing sugars. Conclusion: The employed biological evaluations point out to promising antimicrobial efficiency of alfalfa plants particularly when stressed.