High Performance Liquid Chromatographic Separation And Identification Of A Toxic Fraction From Aloe Barbadensis Miller Leaf Gel Using The Artemia Nauplii Bioassay

Abstract

The current study was undertaken to detect toxicity in purified Aloe vera gel fractions using the Artemia nauplii lethality bioassay, thereby allowing for the identification of compounds of interest for further investigation. The work presented here therefore seeks to not only detect toxicity in gel extracts, but also to assign this toxicity to individual fractions. Methanol extraction and RP-HPLC were used to purify fractions from Aloe vera gel leading to the isolation of 13 major components. Of these 13 fractions tested using the Artemia nauplii lethality bioassay, one proved to be toxic with a 24 h LC50 of 435 姠mL-1. Compared to the tested reference toxins, this Aloe vera gel fraction was approximately three times more toxic than the organophosphate insecticide Mevinphos (24 h LC50 1336 姠mL-1) and approximately six fold less toxic than potassium dichromate (LC50 73 姠mL-1). Of particular interest was the rapid onset of toxicity against the Artemia nauplii. Dilutions of the gel extract were capable of causing 100% mortality within 90 min. The isolated fraction induced 100% mortality within 120 min at a concentration of approximately 800 姠mL-1. In contrast, greater than 36 h was required for Mevinphos and 18 h for potassium dichromate to produce 100% mortality, even at high concentrations (2000 姠mL-1 or 800 姠mL-1 respectively). These results confirm the presence of toxic compounds in Aloe vera gel. As this bioassay correlates well with pesticidal activity and cytotoxic activity in some human tumors, this bioactive fraction may hold promise as a natural pesticide and/or antitumoral agent.