LC-ESI-QTOF/MS characterization of bioactive compounds from black spices and their potential antioxidant activities

Black pepper (Piper nigrum L.), black cumin (Nigella sativa L.) and black cardamom (Amomum subulatum) are considered as important spices, seasoning and folk medicines. They have a diverse range of bioactive compounds, especially for polyphenolic compounds. These polyphenolic compounds contribute to the putative health benefits of these black spices. The purpose of this study was to identify, characterize and quantify the phenolic profile of these black spices using LC-ESI-QTOF/MS and HPLC–PDA and to access their antioxidant potential. The LC-ESI-QTOF/MS analysis led to the identification of 138 phenolic compounds in three black spices. In HPLC–PDA, the p-hydroxybenzoic acid was the most predominant phenolic acid in black pepper and black cumin while diosmin was the most abundant flavonoid in black cardamom (> 20 mg/g). Furthermore, black spices were systematically measured for their TPC, TFC and TTC followed by measurement of their antioxidant activities using DPPH, FRAP and ABTS assays. Black pepper showed the highest TPC, TFC, TTC, DPPH and ABTS activities as compared to other black spices while black cardamom exhibited the highest FRAP activity. The obtained results highlight the importance of these black spices as promising sources of phenolic compounds and they could be potentially utilized in food, feed and nutraceutical industries.