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Dyslipidemias are one of the risk factors for cardiovascular diseases, the leading cause of death and hospitalization worldwide. One way to control cholesterol levels is to control the exogenous cholesterol intake in the body. Natural polyphenolic compounds, namely theaflavins from plant extracts such as black tea, showed the ability to inhibit the formation of the micellar structure, essential for the absorption of cholesterol in the intestine. There are several methodologies to determine this effect, many of which are expensive and time-consuming. Due to these facts, the main purposes of this work were to optimize an inexpensive colorimetric method to study, in vitro, the micellar solubility of cholesterol and applied it to plant extracts. In this work, Cymbopogon citratus leaf extracts, its phenolic fractions, and flavonoids were evaluated. The non-delipidified infusion (CcI) obtained a maximum percentage of micelle destruction of 59.22% for a concentration of 50 μg/mL and the delipidified infusion (CcdI) obtained a maximum percentage of micelle destruction of 58.01% for a concentration of 200 μg/mL. In the case of the fraction of phenolic acids (CcPAs), 23.85% of maximum micellar destruction was recorded for the concentration of 100 μg/mL, while for the fraction of flavonoids (CcF), the micellar destruction was 92.74% at 1 μg/mL, and for the tannin fraction (CcT) of 99.45% at 25 μg/mL. Luteolin presented a percentage of micelle destruction of 94.83% in the concentration of 1 ng/mL, followed by luteolin-7-O-glucoside with 93.71% and luteo-lin-6-C-glucoside with 91.26% at the concentrations of 25 ng/mL and 50 ng/mL, respectively. These results suggest the capability of polyphenols from Cymbopogon citratus to prevent the cholesterol absorption in the gut by micellar destruction, and its contribution for cholesterol-lowering activity.

Ethnopharmacological relevance Leaves extracts from Cymbopogon citratus (DC) Stapf. are widely used in traditional medicine exhibiting several in vivo biological activities, including antidiabetic. Several flavonoids, including aglycones and glycosides, were reported in this plant and previous studies suggested that flavonoids may interact with targets related to diabetes. Aim of the study Evaluated the hypoglycemic activity of C. citratus flavonoids through α-glucosidase inhibition and assess the structure-activity relationship using molecular docking studies. Material and methods An infusion of C. citratus leaves and its flavonoid-rich fraction were prepared. Five flavonoids from this fraction were isolated and structurally characterized by UV spectral analysis with shift reagents, HPLC-PDA-ESI/MSn and 1H NMR. The antidiabetic potential of C. citratus infusion, its flavonoid-rich fraction, glycosylated flavonoids and aglycones was evaluated trough the in vitro inhibition of yeast α-glucosidase. Posteriorly, molecular docking of the tested flavonoids was performed to investigate its possible interactions with the α-glucosidase pocket. Results The infusion of C. citratus, its flavonoid-rich fraction, luteolin and five flavone glycosides namely, luteolin 6-C-β-glucopyranoside (isoorientin), luteolin 7-O-neohesperidoside (ionicerin), luteolin 7-O-β-glucopyranoside (cynaroside), Luteolin 2″-O-rhamnosyl-C-(6-deoxy-ribo-hexos-3-ulosyl) (cassiaoccidentalin B), luteolin 6-C-α-arabinofuranosil-(1→2)-α-L-rhamnopyranoside (kurilesin A) showed higher inhibitory activity than the reference drug. This activity increased by the addition of a sugar moiety. However, the di-glycosides were less active than mono-glycosides. The docking studies showed interactions of sugar moieties and A or B rings with the catalytic pocket mainly through hydrogen bonds. Conclusions Our results corroborate the potential of C. citratus as a medicinal plant for the treatment of diabetes and revealed that its flavonoid glycosides has hypoglycemic effect and can be explored as drug candidates to act as α-glucosidase inhibitors in the treatment of diabetes.