Aloe arborescens Mill’s extracts have been explored for antibacterial and antioxidant efficacies. However, there is limited information on its chemical composition and mechanism of action. The purpose of this study was to assess the chemical composition, antibacterial and antioxidant activities and mechanism of the whole leaf extract of A. arborescens Mill. The phytochemical profile was analysed with gas chromatography mass spectrometry (GC-MS). The antioxidant and antibacterial activities were screened using 1,1diphenyl2picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and micro-dilution assays, respectively. The effects of the extract on the bacterial respiratory chain dehydrogenase, membrane integrity and permeability were analysed using iodonitrotetrazolium chloride, 260 absorbing materials and relative electrical conductivity assays. GC-MS spectrum revealed 26 compounds with N,N’-trimethyleneurea (10.56%), xanthine (8.57%) and 4-hexyl-1-(7-ethoxycarbonylheptyl)bicyclo[4.4.0]deca-2,5,7-triene (7.10%), being the major components. The extract also exhibited antioxidant activity with median concentration (IC₅₀) values of 0.65 mg/mL on DPPH and 0.052 mg/mL on ABTS. The extract exhibited minimum inhibitory concentration (MIC) values ranging from 0.07 to 1.13 mg/mL. The extract inhibited the bacterial growth by destructing the activity of the respiratory chain dehydrogenase, membrane integrity and permeability. Therefore, the leaf extract has the potential to serve as a source of antibacterial and antioxidant compounds.

The constant increase in drug resistance, occurrence of incurable diseases and high medical costs, have necessitated bio-prospecting of fungi as alternative sources of therapeutic compounds. This study aimed at assessing the antibacterial effect and mode of action of secondary metabolites from fungal endophyte associated with Aloe ferox Mill. Endophytic fungus was isolated from the gel of A. ferox and identified by internal transcribed spacer (ITS) rRNA gene sequence analysis. The targets of antibacterial activity were assessed based on minimum inhibitory concentration (MIC) and the effect of the extract on respiratory chain dehydrogenase (RCD) and membrane integrity. Fourier transform-infrared spectrophotometer (FTIR) was employed to ascertain functional groups. The fungus with the most promising antibiotic-production was identified as Aspergillus welwitschiae MK450668.1. Its extract exhibited antibacterial activity with the MIC values of 0.5 and 1 mg/mL against Staphylococcus aureus (ATCC 25925) and Escherichia coli (ATCC 25922). It demonstrated the inhibitory effect on the RCD activity and destruction of membrane integrity on the test bacteria. FTIR spectrum revealed hydroxyl, amine and alkene groups. A. welwitschiae MK450668.1 serves as a potential source of effective compounds to combat the challenge of drug resistance.