PubMed · 16099348
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Paolo D Pigatto, Gianpaolo Guzzi. Aloe linked to thyroid dysfunction.. https://doi.org/10.1016/j.arcmed.2005.03.022
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Aloe vera has wide spread use in health products, and despite several reports on the whole plant and inner gel, little work has been performed on the leaf exudate. Our aim was to evaluate the in vitro efficacy of Aloe vera leaf exudate (AVL) in leishmaniasis. Irrespective of the disease manifestation, promastigotes from strains responsible for cutaneous, mucocutaneous, and visceral leishmaniasis were susceptible to AVL and their IC(50) ranged from 100 to 180 microg/ml. In axenic amastigotes cultured from a L. donovani strain 2001 responsible for visceral leishmaniasis, the IC(50) was 6.0 microg/ml. AVL caused activation of host macrophages evident by an increased release of members of reactive oxygen species that was attenuated by preincubation with free radical scavengers. Collectively, our data indicates that AVL, via its direct leishmanicidal activity which can be further enhanced by activation of host macrophages, is an effective antileishmanial agent meriting further pharmacological investigations.
Aloe vera whole leaf extracts are incorporated into a wide variety of topically applied commercial products. Aloe vera whole leaf extracts may contain anthraquinones, which have been shown to generate reactive oxygen species in the presence of ultraviolet A (UVA) light. Exposure to UVA light alone can also generate reactive oxygen species and is associated with photo-damaged and photo-aged skin in humans. This paper examines the photochemical properties of two Aloe vera whole leaf extracts that differed in their anthraquinone content. In the presence of methyl linoleate, the UVA irradiation of Aloe vera leaf extracts induced lipid peroxidation. The amounts of lipid peroxides formed were higher in the Aloe vera leaf extract that contained lower amounts of anthraquinones. Superoxide dismutase and sodium azide inhibited and deuterium oxide enhanced the formation of lipid peroxides, suggesting that singlet oxygen and superoxide were involved in the mechanism. Spin trapping electron spin resonance (ESR) spectroscopy was used to investigate the generation of free radicals by the UVA photo-irradiated Aloe vera plant extracts. ESR measurements indicated that the UVA photo-irradiation of Aloe vera plant extracts produced carbon-centered free radicals. These results suggest that humans exposed to products that contain Aloe vera whole leaf extracts may have enhanced sensitivity to ultraviolet light.
The aim of this study was to determine in vitro the potential of Aloe Vera juice as a skin permeation enhancer; a secondary aim was to probe the extent to which Aloe Vera itself permeates the skin. Saturated solutions of caffeine, colchicine, mefenamic acid, oxybutynin, and quinine were prepared at 32 degrees C in Aloe Vera juice and water (control) and used to dose porcine ear skin mounted in Franz diffusion cells with water as receptor phase. Receptor phase samples were taken over a 48 h period and permeants determined by reverse-phase HPLC. For caffeine and mefenamic acid no significant enhancements occurred between Aloe Vera and water as vehicles (p>0.05). However, for colchicine, oxybutynin and quinine the presence of Aloe Vera within the formulation provided enhancements (p < or = 0.05). Enhancement potential was dependent upon the molecular weight of the drug in formulation, with the enhancement effect attributable to as yet unidentified components within the Aloe Vera. Colchicine, with a molecular weight of 399.44, achieved the best enhancement with an enhancement ratio of 10.97. No correlation with lipophilicity was apparent. In a further experiment, where freeze-dried Aloe Vera was reconstituted at 200% residue level, permeation of quinine was 2.8 x that from normal Aloe Vera, providing further evidence for the presence of an enhancing factor within Aloe Vera. Certain, although unidentified, components of Aloe Vera readily permeated skin and the relative amount by which they permeated skin was inversely related to the molecular weight of the drug in solution, thus enhancement ratio. A new mechanistic rationale is proposed whereby larger drug solutes inhibit the permeation of Aloe Vera components, but also are then able to interact more effectively with the enhancing factor and be subject to the pull effect.