Inhibitory effect of Mexican oregano (Lippia graveolens Kunth)extracts on digestive enzymes in vitro, and beneficial impact on carbohydrates and lipids absorption in vivo

Ethnopharmacological relevance: Although Mexican oregano inhibits digestive enzymes in vitro its effect on the absorption of carbohydrates and lipids in vivo has not been addressed. Aim of the study: Assess the effect of Mexican oregano (Lippia graveolens Kunth)on carbohydrates and lipids absorption in vivo. The antioxidant activity also was investigated. Materials and methods: Enzymatic inhibitory action of lipase, ?-amylase, and ?-glucosidase was evaluated in vitro. Oral lipid (OLTT)and starch tolerance tests (OSTT)were conducted with L. graveolens acetone (O-A)and ethanol (O-E)extracts (at 102 mg/kg body weight equivalent to a 1 g human doses)in male Wistar rats. The antioxidant activity was evaluated through inhibition of lipid peroxidation and scavenging radical. Results: Both extracts exhibited higher inhibitory median concentration (IC50)of lipase activity (1.9 ?g/?L for O-E and 1.8 ?g/?L for O-A)than the positive control (Orlistat)(0.07 ?g/?L). The IC50 of ?-amylase was higher (41.8 ?g/?L for O-E and 25.2 ?g/?L for O-A)than the Acarbose (2.5 ?g/?L); while ?-glucosidase results showed not statistically differences between groups (?1.7 ?g/?L). The OLTT results showed that both extracts significantly reduced serum triglycerides (?147 mg/dL for O-E and ?155 mg/dL for O-A)as compared with negative control group (only lipid load). In the OSTT, glucose levels showed a significant decrease (?31 mg/dL for O-E and ?17 mg/dL for O-A)than the negative control group (only starch load). About in vitro antioxidant evaluation, not statistically differences between extracts and positive control (Trolox)were observed for scavenged free radicals (?2.0 ?g/?L); whereas O-A inhibited lipid peroxidation similar to the Trolox (?0.8 ?g/?L IC50). The main chemical composition of both extracts was coumaric acid, luteolin, rutinoside, naringenin, and carvacrol. Conclusions: Both extracts reduce lipid absorption; whereas O-E decreases carbohydrate absorption in vivo. Both extracts inhibit lipid peroxidation and scavenging free radicals in vitro.