Abstract
The results from this study revealed that crude extracts isolated from bacterial endophytes obtained from Crinum macowanii bulbs showed activity against both Gram‐positive and Gram‐negative pathogenic bacteria, while Acinetobacter guillouiae crude extracts displayed anticancer activity. This study aimed to isolate and characterize bacterial endophytes and their crude extracts from C. macowanii bulbs. Endophytes were isolated using validated surface sterilization techniques, followed by phenotypic and genotypic profiles of the isolates. Crude extracts were extracted from the endophytes using ethyl acetate, while methanol:dichloromethane (1:1) was used to obtain crude extracts from the bulbs. Antibacterial activity of crude extract from each endophyte was investigated against selected pathogenic strains using the broth microdilution method, and anticancer activity against U87MG glioblastoma and A549 lung carcinoma cells was determined by the MTS (3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxy‐phenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium) assay. Acinetobacter guillouiae, Pseudomonas moraviensis, Pseudomonas sp., Rahnella aquatilis, Bacillus cereus, Novosphingobium sp., Raoultella ornithinolytica, and Burkholderia tropica were successfully isolated. The crude extracts from the majority of endophytes showed antibacterial activity, ranging from 0.125 to >16.00 mg/ml against Gram‐negative and Gram‐positive pathogenic bacteria. Acinetobacter guillouiae extracts showed a high bioactive potential against U87MG glioblastoma cell lines by reducing their growth by 50% at concentrations of 12.5, 6.25, and 3.13 µg/ml. Crude extracts isolated from C. macowanii bulbs showed potential for possible drug lead against common pathogenic bacteria.
Highlights
Crinum macowanii Baker, from the Amaryllidaceae family, is a bul‐ bous plant which has been used traditionally to treat a number of different ailments (Watt & Breyer‐Brandwijk, 1962)
There are a number of studies validating the antimicrobial properties of Crinum species (Maroyi, 2016), overharvesting and overuse of medicinal plants such as C. macowanii has led to overexploitation and extinction of some of these plants (Wyk & Prinsloo, 2018)
The results obtained in this study indicate the inhibition of B. cereus, S. epidermidis, and M. smegmatis at 0.500 mg/ml, 0.125 mg/ml, and 0.500 mg/ml, respectively, which concur with the previous study of Sebola et al (2016)
Summary
Crinum macowanii Baker, from the Amaryllidaceae family, is a bul‐ bous plant which has been used traditionally to treat a number of different ailments (Watt & Breyer‐Brandwijk, 1962). Bioactive secondary metabolites obtained in this way could be alternative sources of therapeutic compounds which could help eradicate problematic infections affecting the human population, for example, antibiotic resistance (Menpara & Chanda, 2013; Tidke et al, 2017). Ek‐Ramos et al (2019) has reported that metabolites produced by endo‐ phytic microorganisms' act as antimicrobial and anticancer agents against human, animal, and plant pathogens and display significant potential in medical and veterinary treatments. With this in mind, the main aim of this study was to isolate and identify bacterial endophytes from C. macowanii bulbs and to explore the role of en‐ dophytic crude extracts as potential antibacterial and anticancer therapeutic agents
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