Modulation of the cell growth by Aloe Vera extract and hydrogen peroxide

Reactive oxygen species (ROS), reactive nitrogen species, and their counterpart antioxidant agents are essential for physiological signaling, while imbalances between oxidants and antioxidants may provoke pathological reactions causing a range of diseases including cancer. In addition, ROS can stimulate signal transduction pathways and lead to activation of key transcription factors such as Nrf2 and NF-κB modulating cell growth and redox balance [1]. The well-known medical plant Aloe vera contains an abundance of antioxidants, which are capable of neutralising ROS [2]. This work evaluates the effects of the genuine Aloe vera extract (AV) on human cells in vitro in respect to the toxic effects of hydrogen peroxide. After propagating Aloe vera for 1 year in 0.5 kg plastic pots, the first fully developed leaf, fourth from the top, was harvested and subjected to biochemical tests for determination of vitamin C, carotenoids and total soluble phenolic content, while total antioxidant capacity of the plant extract was analysed using Brand-Williams method [3]. Afterwards, four different human cell lines, notably HeLa (human cervical cancer), HMEC (human microvascular endothelial cells), HaCat (human keratinocytes) and HOS (human osteosarcoma) were treated with 2 concentrations of AV for 1 hour after one hour pre-treatment with ranging concentrations of H 2 O 2 , thus inducing oxidative stress. The viability of the cells was determined by an MTT-based vitality assay, EZ4U (Biomedica, Vienna, Austria). The plant extract expressed strong antioxidant capacities (1.1 mmol of Trolox eq./g FW), mostly likely due to the combined effects of its antioxidants ingredients. However, while H 2 O 2 inhibited in a concentration dependent manner the growth of all cell lines except HOS, the extract of AV did not show any particular effects except a slight stimulation of the HeLa and HMEC cells. We may assume that antioxidants of the plant extract are not involved in the observed growth modifying effects on the different cell lines used. More likely, some components of the plant extract could interfere with the cellular antioxidants and redox signalling and its effects together with hydrogen peroxide. The above actions of AV confirmed that it can potentially act as relatively safe natural source of medical remedies since there were no toxic effects observed, while further studies on the mechanisms of its actions are needed.