Identification of antioxidant and antimicrobial compounds from the oilseed crop Ricinus communis using a multiplatform metabolite profiling approach

Abstract

Ricinus communis is an important oilseed crop, which is widely used by traditional communities due to its medicinal properties. The extracts obtained from this plant are used to treat rhinitis, chest inflammation, bronchitis, dental caries, scabies, skin diseases, and infections in the digestive apparatus. Despite all its medicinal properties, there is a lack of studies that apply advanced chemical profiling techniques to characterize the chemical diversity of these extracts. The objective of this study was to apply a detailed multiplatform-based metabolite profiling approach to identify antioxidant and antimicrobial compounds in R. communis extracts. Leaf, stem and root extracts were obtained by maceration in hexane, ethyl acetate and ethanol. Antioxidant activity was assessed by the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay and total phenolic compounds were quantified by Folin-Ciocalteu method. Antimicrobial activity was assessed against Bacillus subtilis, B. cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonela choleraesuis, Candida albicans and C. glabrata. Nuclear magnetic resonance, liquid chromatography–mass spectrometry, and gas chromatography–mass spectrometry were used to characterize the chemical profile of the extracts. The antioxidant activity (IC50) of the extracts ranged from 31.73 ± 2.59 to 571.74 ± 45.92 μg mL−1, whereas total phenolic content varied from 16.96 ± 0.30 to 135.06 ± 1.69 mg GAE/g of extract. Extracts obtained with ethanol showed the greatest antioxidant activity, the highest total phenolic content, along with the most promising antimicrobial properties. For example, the ethanolic extract of the leaves showed antimicrobial activity against P. aeruginosa, S. choleraesius, and C. albicans, whereas the ethanol extract of the roots showed antimicrobial activity against P. aeruginosa and C. albicans. Three metabolites were annotated and quantified by NMR, 54 by LC–MS, and 36 by GC–MS, which included alkaloids, fatty acids, terpenes, phenolic compounds, steroids and carotenoid derivatives. The ethanol extract of the leaves showed high levels of the alkaloid ricinine, which seems to contribute for the activities of this extract. This approach allowed us to identify antioxidant and antimicrobial present in R. communis extracts. Therefore, providing important leads into the discovery of new active compounds and possibly to the development of new pharmaceuticals.