Correlations between phytochemical fingerprints of Moringa oleifera leaf extracts and their antioxidant activities revealed by chemometric analysis

Introduction Moringa oleifera Lam. is widely cultivated and applied in tropical and subtropical areas. Numerous studies have been focused on the antioxidant capacity of M. oleifera leaves, but its correlated bioactive phytochemicals remain elusive. Objective In order to search for the corresponding chemical compounds from M. oleifera leaves responsible for their antioxidant activity, the correlations between phytochemical fingerprints of 15 batches of M. oleifera leaves and their antioxidant activities were investigated by using chemometric analysis. Material and Methods Fifteen batches of M. oleifera leaves were extracted with 90% ethanol solution, and their phytochemical fingerprints and antioxidant activities were estimated by using high-performance liquid chromatography-ultraviolet-electrospray ionisation tandem mass spectrometry (HPLC-UV/ESI-MS/MS), and three detected methods, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 2,2 '-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) assay and ferric-reducing antioxidant power (FRAP) assay, respectively. Chemometric analysis was then applied to reveal the correlations between their phytochemical fingerprints and corresponding antioxidant capacity. Results Fifteen M. oleifera leaf extracts exhibited strong antioxidant activities, in which 24 common compounds were identified by LC-MS. Furthermore, the partial least squares (PLS) analysis indicated that compounds 14, 16, 18 and 23 were the main potential effective components in at least two antioxidant tests. They were identified as kaempferol 3-O-rutinoside, quercetin 3-O-(6 ''-malonyl-glucoside), kaempferol 3-O-glucoside, and quercetin derivative, respectively. Conclusion The correlations between phytochemical fingerprints of M. oleifera leaf extracts and their corresponding antioxidant capacities were revealed by chemometric analysis, which provides an alternative method for screening for potential bioactive compounds with antioxidant capacity from M. oleifera leaves.