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

Abstract

Ethnopharmacological relevanceAlthough 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 studyAssess the effect of Mexican oregano (Lippia graveolens Kunth) on carbohydrates and lipids absorption in vivo. The antioxidant activity also was investigated. Materials and methodsEnzymatic inhibitory action of lipase, α-amylase, and α-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. ResultsBoth extracts exhibited higher inhibitory median concentration (IC50) of lipase activity (1.9 μg/μL for O-E and 1.8 μg/μL for O-A) than the positive control (Orlistat) (0.07 μg/μL). The IC50 of α-amylase was higher (41.8 μg/μL for O-E and 25.2 μg/μL for O-A) than the Acarbose (2.5 μg/μL); while α-glucosidase results showed not statistically differences between groups (∼1.7 μg/μL). 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 μg/μL); whereas O-A inhibited lipid peroxidation similar to the Trolox (∼0.8 μg/μL IC50). The main chemical composition of both extracts was coumaric acid, luteolin, rutinoside, naringenin, and carvacrol. ConclusionsBoth extracts reduce lipid absorption; whereas O-E decreases carbohydrate absorption in vivo. Both extracts inhibit lipid peroxidation and scavenging free radicals in vitro.