In vitro and in silico studies on clinically important enzymes inhibitory activities of flavonoids isolated from Euphorbia pulcherrima

Introduction: The genus Euphorbia is known to contain diterpenoids, and several isolated compounds which exhibited biological activities including significant multidrug resistance reversal effects. This work is focused on the isolation, in vitro and in silico studies of two natural bio-active flavonoids (1 & 2) isolated from Euphorbia pulcherrima bark for the very first time. Methods: The phytochemical investigation resulted in the identification of two flavonoids: 3,5,7-trihydroxy-2-(4-hydroxy-3-methoxyphenyl)-6-methoxy-4H-chromen-4-one (1) and 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-6-methoxy-4H-chromen-4-one (2), which were isolated for the first time from Euphorbia pulcherrima. Results: The chemical structures of the two isolated compounds were confirmed by (1)H NMR, (13)C NMR, and ESI-HRMS spectral data. The Bioactivity activity of these compounds was evaluated; results revealed that compounds 1 & 2 exhibit promising urease inhibitory potential with IC50 values of 15.3 ± 2.13 μM and 19.0 ± 2.43 μM, respectively, whereas the positive control thiourea had an IC(50) of 21.0 ± 0.23 μM. Similarly, these compounds were also evaluated against the tyrosinase enzyme; results showed that compound 1 displays significant inhibitory activity with an IC(50) value of 48.7 ± 2.19 μM, whereas compound 2 exhibited a moderate effect with an IC50 value of 74.8 ± 1.79 μM, when compared with the standard (alpha-kojic acid, IC(50) = 47.6 ± 0.67 μM). Additionally, compounds 1 and 2 also exhibited anti-glycation and phosphodiesterase inhibitory activities. Conclusion: Studies dealing with the drug like properties such as in silico screening (docking study) was also carried out to discover the structural features of both compounds 1 and 2. Results indicated that the docking scores of compounds 1 and 2 are in agreement with their IC(50) KEY MESSAGES: Isolation and characterization of two bioactive flavonoids (1 and 2) from Euphorbia pulcherrima. In silico and in vitro enzyme inhibition studies were conducted to identify the therapeutic potential of flavonoids 1 and 2. Drug-like properties were calculated to discover important pharmacophoric features.