No abstract

No abstract

Microbial infections are increasing worldwide, and the widespread emergence of antibiotic-resistant pathogens poses a severe threat to public health. Medicinal plants are well-known sources of bioactive ingredients. This study was designed to determine the antimicrobial and antioxidant activities of extracts from Platycerium stemaria. The serial exhaustive extraction method using a solvent of increasing polarity from nonpolar (hexane) to polar (water) was designed to prepare crude extracts; liquid-liquid partition was used to fractionate of active extracts. The extracts and fractions were screened for antimicrobial activity on bacteria and yeasts using the microdilution method. The antioxidant activity was done using DPPH and FRAP assays. Out of the sixteen extracts screened, four (PsHex, PsH2O(H), PsMeOH(EA), and PsMeOH) exhibited potency with minimal inhibitory concentration (MIC) values ranging from 31.25 to 500 μg/mL. Out of the four extracts, two, including PsMeOH and PsMeOH(EA), exhibited DPPH radical scavenging activity with the antiradical power of 8.94 × 10 − 5 and 47.96 × 10 − 5 , respectively, and ferric reducing antioxidant power values ranging from 0.34 to 61.53 μg equivalent Vit C/g of extract. The phytochemical screening of the promising crude extracts revealed flavonoids, glycosides, phenols, tannins, terpenoids, saponins, and anthraquinones. This study reports the antimicrobial and antioxidant activities of P. stemaria for the first time. The results showed that the serial exhaustive extraction approach used in this study allowed capturing the antimicrobial and antioxidant metabolites beyond the single extraction, indicating the need for a rigorous choice of an appropriate solvent and method for extracting P. stemaria. Further investigation is needed to characterize the active ingredients present in the promising extracts.

Background Bacterial wilt caused by Ralstonia solanacearum (syn. Pseudomonas solanacearum) is the most devastating bacterial disease of tomato (Solanum lycopersicum L.) occurring in tropical zones with consequential substantial yield losses in production fields. Currently, microbial technology in cropping systems has directed investigations toward biological control agents (BCAs), emphasizing the use of plant endophytes, including bacteria. The present work aimed to evaluate the potential of endophytic bacteria from Euphorbia antiquorum L. to suppress bacterial wilt incited by R. solanacearum in plants. Results Of the 10 endophytic species screened in vitro for their antagonistic activity, 6 exhibited promising potency with minimum inhibitory concentration (MIC) values ranging from 62.50 to 7.81 µg/ml. These species also produced cell wall-degrading enzymes (amylase, protease and cellulase), ammonia, siderophores, indole acetic acid and salicylic acid. The 3 most potent species (B. amyloliquefaciens CBa_RA37, B. velezensis CBv_BE1 and B. amyloliquefaciens CBa_BFL2) enhanced the germination of tomato seeds and protected young tomato plantlets from the devastating effects caused by R. solanacearum infection. Conclusions This investigation demonstrated that these endophytic bacteria from E. antiquorum L. endowed with the ability to improve the growth and protection of tomato plants could be further developed as potential biopesticides to help mitigating the effect of bacterial wilt in tomato farms. Further investigation will set the baseline for formulation and evaluation of their efficacy in the open field.