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Deciphering the phenolic acid reserves and antioxidant activity within the protocorm like bodies of Ansellia africana: A vulnerable medicinal orchid

Bhattacharyya, Paromik, Kumar, Vijay, Grúz, Jiri, Doležal, Karel, Van Staden, Johannes
Industrial crops and products 2019 v.135 pp. 21-29
Orchidaceae, acetic acid, acetylcholinesterase, antimicrobial properties, benzoates, bioaccumulation, biomass, cinnamates, enzyme inhibition, high performance liquid chromatography, medicinal plants, models, oxygen radical absorbance capacity, phenolic acids, picloram, plant extracts, reactive oxygen species, secondary metabolites, tandem mass spectrometry, thidiazuron, Africa
In the past few decades, significant strides have been made in the domain of phytomedicines. Amongst the various medicinal plant taxa exploited for that purpose, orchids are an important representative. Ansellia africana is one such candidate taxon, which has incessantly been used in various herbal preparations for centuries. Having distributions in various parts of Africa, the plant is having potent acetyl cholinesterase inhibitory as well as antimicrobial activity. The protocorm like-bodies (PLBs) were induced by a synchronized influence of both meta-topolin (mT) and thidiazuron (TDZ) along with 1-napthalene acetic acid (NAA) and the best result was achieved at 5 μM TDZ + 15 μM mT and 5 μM NAA. Besides, the effects of six plant growth regulators (PGRs) [meta-topolin (mT); meta-topolin riboside (mTR); 6,3-methoxybenzylaminopurine (MemT) and 6,3-methoxybenzylamino-9-b-D-ribofuranosylpurine (MemTR); TDZ and picloram] on the levels of phenolic acid accumulation in the protocorm-like bodies (PLBs) biomass were assessed using the ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Coupled with that, the antioxidant potentials of the cultured biomass under various PGR treatments were also analyzed using the oxygen radical absorbance capacity (ORAC) technique. mT derivatives (mTR and MemTR) and TDZ significantly improved the synthesis and bioaccumulation of both benzoates and cinnamates in the cultured PLB biomass in comparison to control, opening a new frontier in secondary metabolite research by using orchids as source material. The highest antioxidant potential based on the oxygen radical scavenging activity (ORAC) model system was obtained in 5 μM mTR. The study strongly implies that A. africana PLBs can be manipulated on a mass scale for the production of phenolic acids exhibiting a high degree of antioxidant activity. Collectively, both PGRs and their concentrations had a comprehensive impact on induction, proliferation, biochemical accumulation of phenolic acids and the subsequent antioxidant activity of the resultant plant extracts. The present study provides important baseline information about utilization of orchid bio resources for production of prized phenolic compounds.