Aloe (Aloe vera) is a cactuslike plant originally indigenous to Africa. Aloe vera is the most prominent among the more than 300 species belonging to this family. It was widely regarded as a master healing plant in folkloric medicine.149 In the last few decades, aloe has gained popularity as an adjunct treatment to heal burns and side effects following radiation therapy. This important application, which correlates with its traditional usage as a remedy to cuts and burns, has gained momentum following reports of a successful treatment of X-ray and radium burns in the 1930s. A large number of published reports support aloe's protective effects against radiation-induced skin injury and radiation ulcers.150'165 A randomized, blinded clinical study with Aloe vera gel exhibited a protective effect in preventing skin reactions in patients undergoing radiation therapy,151 whereas two other phase III clinical studies found no significant protective effect with Aloe vera treatment.152 Aloe was found to be antibacterial and antifungal. It increases blood flow to wounded areas and stimulates fibroblasts, the skin cells responsible for wound healing.
Aloe exhibited antitumor,153 anticarcinogenic,154 and cancer chemopreventive155 properties in animal models. According to a Russian report, treatment of experimental tumors in mice and rats with aloe juice contributed to reduction of tumor mass, metastatic foci, and metastasis frequency.156 Bioassay-guided purification of an aloe species afforded a hydroxyanthraquinone compound called aloe-emodine, which significantly inhibited P-388 lymphocytic leukemia and human neuroectodermal tumors implanted in mice.157 158 It also inhibited human hepatoma cell lines,159 Hep G2 and Hep 3B, human Merkel cell carcinoma,160 and human lung squamous cell carcinoma161 cell lines in cultures. The tumor-prevention and anticancer activities of aloe are due mostly to the immune stimulation and immune modulation through activation of macrophages (antigens), causing the release of substances like interferons, interleukines, and tumor necrosis factor.162 Aloe vera gel inhibited angiogenesis, a process of forming new blood vessels to feed the tumor.163 It also potentiated the effects of 5-fluorouracil and cyclophosphamide in combination therapy.156
The only clinical study on record on the antitumor activity of Aloe vera demonstrated that an aloe and melatonin combination might delay the onset of metastasis in patients with advanced-stage solid tumors, including breast cancer.164 Aloe is very safe when applied either orally and topically, and it also appears to be safe when injected in high doses. The FDA's approval of Aloe vera as a flavoring agent is a further indication of its safety.165 The benefits associated with the use of aloe may provide great impetus to the research community to design and implement further controlled studies on this important plant.
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