Medicinal Mascarene Aloes: An audit of their phytotherapeutic potential.

A phytochemical and biological investigation of the endemic Mascarene Aloes (Aloe spp.), including A. tormentorii (Marais) L.E.Newton & G.D.Rowley, A. purpurea Lam, A. macra Haw., A. lomatophylloides Balf.f and A. vera (synonym A. barbadensis Mill.), which are used in the traditional folk medicine of the Mascarene Islands, was initiated. Methanolic extracts of the Aloes under study were analysed using high resolution LC-UV-MS/MS and compounds belonging to the class of anthraquinones, anthrones, chromones and flavone C-glycosides were detected. The Mascarene Aloes could be distinguished from A. vera by the absence of 2″-O-feruloylaloesin and 7-O-methylaloeresin. GC-MS analysis of monosaccharides revealed the presence of arabinose, fucose, xylose, mannose and galactose in all the Mascarene Aloes and in A. vera. The crude extracts of all Aloes analysed displayed antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Only extracts of A. macra were active against P. aeruginosa and Klebsiella pneumoniae, while none of the Aloe extracts inhibited Propionibacterium acnes. A. macra displayed anti-tyrosinase activity, exhibiting 50% inhibition at 0.95mg/mL, and extracts of A. purpurea (Mauritius) and A. vera displayed activity in a wound healing-scratch assay. In vitro cytotoxicity screening of crude methanolic extracts of the Aloes, using the MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) showed that only A. purpurea (Réunion) elicited a modest toxic effect against HL60 cells, with a percentage toxicity of 8.2% (A. purpurea-Réunion) and none of the Aloe extracts elicited a toxic effect against MRC 5 fibroblast cells at a concentration of 0.1mg/mL. Mascarene Aloe species possess noteworthy pharmacological attributes associated with their rich phytochemical profiles.

Bio-prospecting endemic Mascarene Aloes for potential neuroprotectants.

The Mascarene Aloes are used in the traditional pharmacopoeia against various ailments including cutaneous diseases and as antispasmodics. Scientific evidence to support these claims is non-existent and mainly based on the scientific repute of A. vera. The antioxidant profile of methanolic leaf extracts of A. purpurea Lam., A. tormentorii (Marais) L. E. Newton & G. D. Rowley, A. lomatophylloides Balf. f., A. macra Haw. and A. vera (L.) Burm. f. was studied using the total antioxidant capacity, copper equivalent and superoxide dismutase assays. In vitro cytotoxicity was evaluated on CAD (Cath.-a-differentiated) neuronal cells by the methyl tetrazolium assay, and the neuroprotective profile was assessed using hydrogen peroxide-induced neurotoxicity with the CAD cells. The aloin and vitexin content were determined by high-performance liquid chromatography with diode-array detection. A. purpurea had the highest aloin content (546.6 nmol/g), while A. tormentorii had the highest vitexin content (67.3 nmol/g). A. macra (concentration <0.1 mg/mL) elicited a 10% cytotoxicity effect on CAD cells while other Mascarene Aloes were not cytotoxic. This study validates the antioxidant and neuroprotective potential of Mascarene Aloes focusing on their aloin and vitexin content that are also present in other reputed medicinal Aloes.

MK-801 increases the baseline level of anxiety in mice introduced to a spatial memory task without prior habituation.

C57BL/6J mice were introduced to a nine arm radial maze without prior habituation and trained in the acquisition of a working memory task in 16 sessions, one session per day. In this maze mice need to climb onto an upward inclined bridge in order to reach and cross onto an arm. They received in each session an i.p. injection of MK-801 (0.1 mg/kg) 30 min before training or immediately after training. MK-801 pre-treated mice made significantly more entries onto the bridges, fewer entries onto the arms and took significantly longer time to make a first arm visit compared to saline and MK-801 post-treated mice during the first 3 session blocks (4 sessions per block). These results indicate that MK-801 induced anxiety which was extended throughout the first 3 session blocks. MK-801 pre-treated mice made also significantly more errors and required more sessions to reach the criterion compared to saline and MK-801 post-treated mice. Administration of MK-801 after training did not affect the acquisition of the task. The present results indicate that MK-801 pre-treatment impaired the acquisition of a spatial task and this can be accounted for by its effect on the baseline level of anxiety which was elevated. The introduction of mice to the acquisition of the task without prior habituation demonstrates that a drug treatment can affect learning and memory by increasing and/or prolonging anxiety. Such effect may be confounded with learning and memory performance and not detected with pre-habituation training procedures, particularly when the number of sessions is determined a-priori.