Multifaceted Biological Activity of Selected Flavone C-Monoglucosides

Determination of the multifaceted activity of selected flavone C-monoglucosides, namely orientin (OR), homoorientin (hOR), vitexin (VT), and isovitexin (iVT) in comparison to quercetin (Q) was addressed. Their antioxidant activity was characterized by the peak oxidation potentials (Epa) provided by the differential pulse voltammetry (DPV) method, whereas their inhibitory activity towards angiotensin converting enzyme (ACE), acetylcholinesterase (AChE), and advanced glycation end-products (AGEs) formation was measured in a model system. The relationship between the multifaceted activity of flavone C-monoglucosides and their Epa was evaluated. The rank of the antioxidant activity in comparison to quercetin was Q > hOR ≈ OR > iVT ≈ VT, whereas the order of the ACE inhibitory activity was Q > hOR > OR > VT > iVT. The correlation between IC₅₀ for ACE inhibition and E_pa values was r = 0.787. This finding was confirmed by the negative correlation between ACE inhibitory activity and antioxidant activity of these compounds (r = -0.838). The order of the AChE enzyme inhibitory activity was hOR > OR > iVT > VT > Q, whereas the rank of anti-AGEs activity was hOR > OR > iVT > Q > VT > AG (aminoquanidine), and the weak positive correlation between IC₅₀ and E_pa was noted (r = 0.546 for BSA (bovine serum albumin)/glucose system and r = 0.580 for BSA/methylglyoxal system). In contrast, the anti-AGEs activity was negatively correlated with IC₅₀ values for ACE inhibition (r = -0.669), whereas no correlation was found between the ACE and AChE inhibitory activities. The results expand our knowledge of the multifaceted activity of flavone C-monoglucosides.