used to treat A. vera adventitious roots cultured on MS liquid media with IBA for five weeks. The production of aloe emodin and chrysophanol was enhanced by the salicylic acid treatment up to 13-fold as compared with control. Ultra performance liquid chromatography- mass spectrometry (UPLC-MS) analysis confirmed the presence of 37 compounds induced by salicylic acid, including aloe emodin and chrysophanol. This analysis also confirmed that these metabolic pathways change the expression of octaketide synthase genes and decreases in malonyl-CoA. In addition, anti-inflammatory activity was enhanced in extracts of salicylic acid-treated adventitious roots. It has been proved that salicylic acid has an important role in induction of the plant-specific type III polyketide biosynthetic pathway and so that the efficacy of A. vera can be increased through salicylic acid treatment (Lee et al. 2013).
The effects of different abiotic elicitors including nano-Ag, nano-TiO2, NH4NO3, and sucrose on cell suspension culture of A. vera were investigated. The maximum production (127-fold) of aloin was obtained with NH4NO3 at 48 hours of treatment. Aloin content was increased with nano elicitors at 48 hours after treatment and decreased gradually after that (Raei et al. 2014). A. barbadensis, the miracle plant, is the most widely cultivated species and has been widely used for medicines and cosmetics. The leaf discs of A. barbadensis were used as explants and maximum callus induction was obtained in MS medium supplemented with 2,4-D and Kin. This combination of growth hormone also increased the anthraquinone production, while NAA and IAA demonstrated very poor response (Supe 2013). Maximum adventitious root induction was observed in MS culture medium with supplementation of NAA and BA with suitable concentrations. The accumulation of phenolic compounds in the media that was adsorbed polyvinylphyrollidine (PVP) analogs for maintaining continuous growth of roots. The aloe emodin contents in various adventitious roots grown by different basal mediums revealed that aloe emodin accumulation is much higher on B5 medium than on MS medium (Lee et al. 2011). Aloesin, aloin, and aloe emodin are considered as the most important secondary products due to its medicinal and cosmetic properties. It was observed that aloesin production was higher in MS medium with 2,4-D and BA supplementation, while total aloin concentration was higher in calli induced by leaves. Aloe emodin production was greater than aloin production in the calli of both basal and fresh leaves compared to the entire leaves. Probably, this high aloe emodin production found was due to the aloin oxidation (Acurero 2008).
Light is considered as important component for induction of calli in A. barbadensis. The maximum calli were induced under the dark condition on MS medium supplemented with NAA, as compared to light. Biotransformation ability of A. barbadensis cell suspension culture was studied by incubation with (+)-adrenosterone, which afforded three products: Δ1-2-dehydroadrenosterone, 5α-androst-1-ene-3,11,17-trione, and 17β-hydroxyandrost-4-ene-3, 11-dione (Badar et al. 2013).
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