Exploring Essential Oils and Their Bioactive Components from Mediterranean Medicinal Plants as Natural Antigiardial Agents

Lamiaceae and Asteraceae plant species have been widely used in traditional medicine to treat gastrointestinal disorders in countries of the Mediterranean basin. Other properties, such as antioxidant, anti-inflammatory, anti-bacterial, anti-parasite, and anti-virus have been described. Giardia duodenalis is the most frequent intestinal protozoon affecting young children worldwide and nitroimidazoles are the main treatment, but non-responding cases are widely reported. In this paper we tested the antigiardial activity of several Lamiaceae and Asteraceae plants. Essential oils from 22 traditional medicinal plants from Lamiaceae and Asteraceae families and its main components were tested against the parasite employing the MTT method. The composition of the essential oils was determined by a metabolomic approach (GC-MS). Transmission Electron Microscopy was used to evaluate morphological alterations. The best antigiardial activity was obtained with the genera Lavandula, Mentha, Thymus, and Satureja, while the best selective indexes were obtained with compounds {gamma}-terpinene, caryophyllene oxide, carvacrol and thymol. Synergies were observed with linalyl acetate + linalool (Lavandula EOs), linalyl acetate + {rho}-cymene or thymol, or combinations of {rho}-cymene, {gamma}-terpinene, thymol, and carvacrol (Satureja EOs). Membranolysis, enlarged periplasmic vacuoles, and loss of the cytoplasmic content were evident effects of {gamma}-terpinene on trophozoites after 1 hour. The present study provides phytotherapeutic evidence of essential oils from species of Lavandula, Mentha, Thymus, and Satureja as natural antigiardial agents, as well as some of their main components, {gamma}-terpinene, caryophyllene oxide, carvacrol and thymol.