No evidence of antiseptic properties and low toxicity of selected Aloe species

Abstract

Background and Aim: Closely related plant species often share similar secondary metabolites and bioactivities and are therefore good targets for bioactivity testing when one or more species within a genus are known to possess therapeutic properties. The genus Aloe has a long history of medicinal usage in many areas of the world. Many species are known to have therapeutic properties, several species of which have well-established antibacterial bioactivities. The current studies examine the toxicity of several Aloe species and their ability to inhibit bacterial growth and compare them to the most extensively studied species, Aloe barbadensis , which has well-established antibacterial bioactivities. Results: A. barbadensis methanolic extract displayed broad spectrum antibacterial activity, inhibiting the growth of 8 of the 14 bacteria tested (57%). It was effective against both Gram-positive and Gram-negative bacteria, inhibiting the growth of 4 of 4 Gram-positive bacteria (100%) and 4 of 10 Gram-negative (40%) bacteria tested, respectively. In contrast, Aloe elgonica, Aloe pruinosa, Aloe chabaudii, Aloe daiyana, Aloe marlothi and Aloe vryheidensis all showed no antibacterial activity toward any of the bacteria tested. All of the Aloe species displayed low toxicity similar to that of the A. barbadensis control. A. daiyana was the most toxic of the Aloe species tested with 24, 48 and 72 hours LC50 values of 1018.2, 517.0 and 405.7 ΅g/ml, respectively. Conclusions: Despite their close taxonomic relationship, A. elgonica , A. pruinosa , A. chabaudii , A. daiyana , A. marlothi and A. vryheidensis do not have the same antibacterial medicinal potential as A. barbadensis , but may still have other similar toxicity-related bioactivities. Testing against protozoa, fungi, virus and tumor cells is required to determine if this is the case.