Antioxidant activity and identification by HPLC-DAD-MS of 3-deoxyanthocyanins in the husks of Sorghum caudatum (L.) Moench grains from Burkina Faso

As indicated by the World Health Organisation (WHO), the resurgence of chronic diseases is projected to account for 70 % of deaths and 56 % of illnesses globally by 2030. In response, authorities are allocating resources towards prevention through the use of substances with natural or synthetic antioxidant properties. However, the safety of synthetic antioxidants is constrained by the limited number of molecules they can be derived from and the necessity for intricate and costly testing to substantiate their safety. In light of this, the scientific community has set itself the objective of identifying new potential sources of natural antioxidants with the more effective capacity in prevetion of these chronic diseases. Anthocyanins, particularly 3-deoxyanthocyanins are cited as one antioxidant molecules with preventive efficacy. The objective of this study is to contribute to the discovery of new sources of 3-deoxyanthocyanins. In order to achieve this objective, a concentrated extract of 3-deoxyanthocyanins was first prepared by maceration of the husks of Sorghum caudatum grains in acidified ethanol, followed by precipitation in acidified distilled water.The Folin-Ciocalteu and differential pH methods were then employed to determine the total phenolic compound content and the total 3-deoxyanthocyanin content of the extract, respectively. The antioxidant potential of the extract was evaluated by determining its free radical scavenging activity using the ABTS method, its reducing power of ferric ions using the FRAP method, and the percentage of hydrogen peroxide (H₂O₂) scavenging. Using physico-chemical and physical methods (PC, HPLC, UV–vis and MS), the 3-deoxyanthocyanins present in the extract from the husks of Sorghum caudatum grains were identified. The results of these analyses demonstrated that the total phenolic compound content was 237.73 ± 2.12 mg GAE/g extract, while the 3-deoxyanthocyanin content was 99.33 ± 4.16 mg EApi/g extract and 110.05 ± 4.33 mg ELt/g extract. The extract demonstrated notable antioxidant activity, with an CI₅₀ of 62.59 µg/mL as determined by the ABTS method, a content of 77.35 ± 0.17 mg TE /g extract as quantified by the FRAP method, and an H₂O₂ scavenging percentage of approximately 72.29 %. The extract was found to contain five distinct compounds, namely luteolinidin, 7-O-methylluteolinidin, 5-O-methylluteolinidin, apigeninidin and 7-O-methylapigeninidin. The grain husks of Sorghum caudatum represent a novel source of 3-deoxyanthocyanins. Consequently, they offer a promising avenue for the extraction of natural antioxidants, natural colouring agents and nutraceuticals for the food industry, thereby enhancing the economic value of agricultural waste and augmenting the profitability of Sorghum cultivation.