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Plant-derived bioactive substances have demonstrated significant qualities that suggest they may be crucial in preventing various chronic diseases. Flavonoids, which include apigenin, are the biggest group of polyphenols. In our study, we aimed to obtain the methanol-chloroform (1:1) extract from the aerial parts of Nepeta baytopii Hedge & Lamond and purify the apigenin using bioactivity-guided isolation to separate the active fraction. The current in vitro study provides updated knowledge on apigenin regarding its previously unresearched DNA protection activity and enzyme inhibition, enzyme inhibition kinetics, and enzyme-apigenin interactions. In this context, these studies will be the first and will contribute to the literature. Apigenin had high urease (IC 50 -5.00 ± 0.00 µM), butyrlcholinesterase (BChE:IC 50 -10.48 ± 0.00 µM), and tyrosinase (IC 50 -177.82 ± 14.40 µM) inhibition activities, while inhibition binding constants were high in urease (K i -0.05 mM), tyrosinase (K i -0.06 mM), and carbonic anhydrase (K i -0.08 mM). The binding affinities and constants of the interaction were also ascertained to be high for BChE (-9.50 kcal/mol, and K i -0.11 µM), and tyrosinase (-8.80 kcal/mol, and K i , 0.62 µM) with apigenin. In summary, apigenin can be used as an inhibitor for five enzymes. These results will give priority to further studies. Apigenin showed high DNA protection activity with a Form I value of 67.37%. These data demonstrated that the interaction formed by BChE-apigenin gave the best results regarding enzyme inhibition and enzyme-molecule interaction. The stability of this complex was evaluated using molecular dynamics modeling.

Parietin was isolated from Xanthoria parietina (L.) Th. Fr.' (methanol:chloroform) extract, using a silica column. 13 C NMR and 1H NMR were used to confirm the structure of the isolated parietin. For the first time, parietin was investigated for its antioxidant, antibacterial and DNA protective activities. Molecular docking was carried out to determine the binding affinity and interactions between the enzymes and our molecule. Inhibition and kinetic mechanism studies for the action of the enzymes were performed too. Parietin exhibited high metal chelating activity. The MIC values of parietin were sufficient to inhibit different bacterial strains; E. coli, P. aeruginosa, K. pneumoniae and S. aureus . Molecular docking applications exhibited that acetylcholinesterase (AChE), butyrylcholinesterase (BChE), lipase, and tyrosinase have high potential for binding with the parietin. Especially, the parietin's highest binding affinity was recorded with AChE and tyrosinase. These results were confirmed by the inhibition and kinetics results, where, parietin observed a potent inhibition with an IC 50 values between 0.013-0.003 µM. Moreover, parietin acts' as a non-competitive inhibitor against AChE, BChE, and lipase, and as a competitive inhibitor against tyrosinase with a high rate of inhibition stability. The promising biological properties of parietin revealed its effectiveness in terms of suitability in the food and pharmaceutical industries.Communicated by Ramaswamy H. Sarma.