Antioxidant and antidiabetic flavonoids from the leaves of Dypsis pembana (H.E.Moore) Beentje & J.Dransf., Arecaceae: in vitro and molecular docking studies

Abstract Background Oxidative stress and diabetes are medical conditions that have a growing prevalence worldwide, significantly impacting our bodies. Thus, it is essential to develop new natural antioxidant and antidiabetic agents. Dypsis pembana (H.E.Moore) Beentje & J.Dransf (DP) is an ornamental palm of the family Arecaceae. This study aimed to broaden the understanding of this plant’s biological properties by evaluating its in vitro antioxidant and antidiabetic activities. Methods The in vitro antioxidant activities of the crude extract, fractions, and selected isolates were evaluated by DPPH method. While the in vitro antidiabetic activities of these samples were evaluated by assessing the degree of inhibition of α-glucosidase. Additionally, molecular docking analysis was performed to investigate the interactions of tested compounds with two potential targets, the cytochrome c peroxidase and alpha glucosidase. Results The crude extract displayed the highest antioxidant activity (IC50 of 11.56 µg/ml), whereas among the fractions, the EtOAc fraction was the most potent (IC50 of 14.20 µg/ml). Among tested compounds, isoquercetrin (10) demonstrated the highest potency, with an IC50 value of 3.30 µg/ml, followed by rutin (8) (IC50 of 3.61 µg/ml). Regarding antidiabetic activity, the EtOAc (IC50 of 60.4 µg/ml) and CH2Cl2 fractions (IC50 of 214.9 µg/ml) showed activity, while the other fractions did not demonstrate significant antidiabetic effects. Among tested compounds, kaempferol-3-O-neohesperidoside (9) showed the highest antidiabetic activity, with an IC50 value of 18.38 µg/ml, followed by kaempferol (4) (IC50 of 37.19 µg/ml). These experimental findings were further supported by molecular docking analysis, which revealed that isoquercetrin and kaempferol-3-O-neohesperidoside exhibited strong enzyme-binding affinities to the studied enzyme targets. This analysis provided insights into the structure-activity relationships among the investigated flavonol-O-glycosides. Conclusion The biological and computational findings revealed that isoquercetrin and kaempferol-3-O-neohesperidoside have potential as lead compounds for inhibiting cytochrome c peroxidase and alpha glucosidase enzymes, respectively

Comparative sorption isotherms for colorants present in Dyers’ madder (Rubia tinctorum L.) provide new insights into historical dyeing

Dyers madder (Rubia tinctorum L.) has been famously used throughout history as a source of red dye. The sorption onto mordanted wool of the major colorant components of R. tinctorum, alizarin and the glycosides ruberythric acid and lucidin primeveroside, is studied herein. Sorption of a purified 1:1 mixture of ruberythric acid:lucidin primeveroside most closely followed a Temkin isotherm (R2 0.925), whereas alizarin followed a Freundlich isotherm (R2 0.940). These results were compared to HPLC chromatograms of English, Turkish and Iranian varieties of R. tinctorum before and after dyeing, where it was observed that the glycosides are shown to have the highest uptake onto wool. The higher sorption energy of the purified 1:1 ruberythric acid:lucidin primeveroside mixture (–11.4 kJ mol-1) compared to alizarin (–5.8 kJ mol-1) is in agreement with the HPLC results, indicating that the ruberythric acid/lucidin primeveroside mixture has a substantially higher affinity for wool compared to alizarin. Not only do the glycosides show higher affinity for the wool, but greater interactions between adsorbed species suggest a more extensive aggregation of dye on the surface of the wool. These observations are in contrast to much literature and bring into question previous conclusions that alizarin was the main dyeing species throughout history