Bio-guided fractionation of the antimutagenic activity of methanolic extract from the fruit of Randia echinocarpa (Sessé et Mociño) against 1-nitropyrene

Abstract

Randia echinocarpa is a native plant from Mexico that produces an edible fruit with several ethnopharmacological uses (e.g. cancer, kidney ailments, and diabetes). Extracts of this fruit have shown antimutagenic activity. In this report, a methanolic extract of R. echinocarpa and a bio-guided chromatographic strategy were used to obtain an hexanic fraction (HF) with strong antimutagenic activity (microsuspension assay with Salmonella typhimurium YG1024) using 1-nitropyrene as mutagen (1-NP, 50 and 100 ng/tube). The HF (500 ng/tube) showed the highest inhibition percentage of mutagenic activity (PI) (75%, 1-NP 50 ng/tube; 84%, 1-NP 100 ng/tube). HF chromatography with silica produced HF₁ which was further separated to produce the fractions with the highest antimutagenic activities (HF_1–1 and HF_1–2, PI ≥ 60%). These fractions were chemically characterized by chromatography and gas chromatography–mass spectrometry; among the main components of HF, HF_1–1 and HF_1–2 were registered linoleic acid, palmitic acid and β-sitosterol, which could be responsible for the antimutagenic activity of R. echinocarpa fruit. The samples evaluated were neither toxic nor mutagenic. Randia echinocarpa is an underutilized plant and its fruit has been used traditionally as food/medicine; fruit consumption could provide human health benefits and it has potential to be exploited under conditions of ecological sustainability.

Introduction

Nowadays, cancer disease represents one of the most important public health concerns. This illness of multifactor etiology can affect every organ and system in the body, and the symptomatology and treatment responses are highly variable. Consequently, early detection and prevention are the best strategies for disease control and new therapeutic/preventive agents are needed (Thun, DeLancey, Center, Jemal, & Ward, 2010).

Plants are the main source of bioactive compounds (Cragg, Grothaus, & Newman, 2009), especially of anticancer compounds. Mexico has a large floristic diversity but it is practically unknown (SEMARNAT, 2008).

Randia is considered as a Neotropical genus with 60 to 70 species; it is distributed from Southern United States to South America and Mexico represents the area of the highest diversity with 33 species (Bye et al., 1991, Lorence and Nee, 1987).

Randia echinocarpa Sessé et Mociño (Rubiaceae) is a shrub or small tree of 2–6 m high, distributed along the Pacific Ocean Shore of Mexico. The fruit of R. echinocarpa is known as “papache”. The pulp of the ripe fruit is dark, with a large number of rounded seeds (see Fig. S1 as supplementary data), the isolated compounds from the fruit of R. echinocarpa are mannitol, β-sitosterol, and quinovic, oxoquinovic, ursolic and oleanolic acids (Bye et al., 1991). R. echinocarpa fruit has a sweet/bitter flavor, it is mainly consumed by people of rural areas as food/medicine, and only commercialized in Mexican traditional markets (Cortés, 2000).

R. echinocarpa has been employed in Mexican traditional remedies for cancer, malaria and diabetes; as well as for kidney, pulmonary, circulatory and gastro-intestinal ailments (Bye et al., 1991, Cortés, 2000). These ethnopharmacological properties have not been scientifically confirmed. On the other hand, a positive effect has been experimentally demonstrated for an aqueous extract of the fruit, it improves the cicatrizing speed in skin of wounded rats (Pérez, Pérez, Pérez-González, & Vargas, 1993); negative effects are also registered for the oral administration of this extract in rats, increased diuretic activity and urolith formation (Vargas Solis & Pérez Gutiérrez, 2002). In a previous report, an aqueous extract of R. echinocarpa fruit (500 μg/tube) showed a moderate antimutagenic activity in the microsuspension assay with YG1024 strain, PI of 32 and 53% at 50 and 100 ng/tube of 1-NP, respectively; remarkably, the extract acts by desmutagenic and bioantimutagenic mechanisms (Santos-Cervantes, Ibarra-Zazueta, Loarca-Pina, Paredes-Lopez, & Delgado-Vargas, 2007).

R. echinocarpa plants were widely distributed along the State of Sinaloa and nowadays their populations have been diminished. Based on the traditional uses of R. echinocarpa, it could be considered an underutilized plant and an improved knowledge about its chemical composition and biological activities will contribute to use this natural resource under conditions of ecological sustainability (Jaenicke & Höschle-Zeledon, 2006).

The objective of this study was to characterize the responsible compounds of the antimutagenicity in the fraction with the highest activity obtained from the crude methanolic extract of R. echinocarpa fruit (ME).