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 wellestablished 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 µg/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.