Phytochemical composition and in -vitro pharmacological evaluation of Emex australis Steinh: A natural source of enzyme inhibitors

The current research investigated the chemical profiling and biological activities of Emex australis Steinh. aerial and fruit parts (methanol and dichloromethane-DCM extracts). Chemical composition was established by determining the amounts of phenolic and flavonoid contents, HPLC-PDA polyphenolic quantification, and UHPLC-MS secondary metabolites profiling to understand the observed biological activities. Antioxidant evaluation was performed utilizing six different assays (DPPH, ABTS, FRAP, CUPRAC, phosphomolybdenum, and metal chelation). Moreover, enzyme inhibition abilities against cholinesterases, α-amylase, α-glucosidase, and tyrosinase were also determined. The fruit methanol extract contained the highest phenolic (157.96 mg GAE/ g extract) and flavonoid contents (41.43 mg QE/g extract), which could justify the observed significant antioxidant (except metal chelating), α-amylase, α-glucosidase, and tyrosinase inhibitory potentials. The other extracts were active against cholinesterases and tyrosinase. The HPLC-PDA polyphenolic analysis quantified a number of 11 phenolic secondary metabolites. The fruit-MeOH extract was found to quantify the maximum phenolics with catechin (4.27 μg/g extract) and gallic acid (4.84 μg/g extract) in higher amounts. Similarly, rutin present in maximum quantity in the aerial-MeOH extract (2.93 μg/g extract). Furthermore, the UHPLC-MS study of aerial and fruit methanol extracts reveals the existence of 22 secondary metabolites, most of which were flavonoid derivatives. Besides that, Pearson coefficient analysis (PCA) was also carried to determine a possible correlation between bioactive contents and observed biological assays. Thus, it is concluded that E. australis extracts contain important classes of secondary metabolites and also exhibited considerable antioxidant and inhibition potential against clinically relevant enzymes.