Determination of Enzyme Inhibitory and Antioxidant Activities of Selected Oak Galls

In this study, the enzyme inhibition and antioxidant activities of methanol extracts obtained from galls induced by Andricus quercustozae and Andricus cecconii on Quercus brantii Lindley. and Andricus quercusramuli on Quercus infectoria Oliver were investigated. The enzyme inhibition activity was assessed using spectrophotometric methods for acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, and urease inhibition. The total phenolic and flavonoid contents of the extracts were quantified as gallic acid and quercetin equivalents, respectively. Antioxidant activity was evaluated using three distinct assays: DPPH free radical scavenging, ABTS cation radical scavenging, and CUPRAC. Regarding cholinesterase inhibition, while none of the extracts exhibited activity against AChE, they demonstrated inhibition of BChE, with A. quercustozae gall extract showing the highest activity (31.33 ± 1.25%). Similarly, in tyrosinase inhibition, A. quercustozae gall extract exhibited the most significant effect, with an inhibition rate of 61.16 ± 0.72%. In urease inhibition, A. quercustozae gall extract was the only sample to demonstrate activity (40.98 ± 1.41%), whereas A. quercusramuli and A. cecconii extracts showed no significant effect. The total phenolic contents of the extracts were higher than their total flavonoid contents, correlating with their strong antioxidant activities. Some extracts exhibited higher antioxidant activity than standard positive controls, further emphasizing their potential as natural antioxidant sources.