Efficient in vitro regeneration with an impetus on chemotypic variation in Spilanthes acmella (L.) Murr

High frequency in vitro regeneration protocol was successfully developed in Spilanthes acmella (L.) Murr., a multipurpose medicinal herb synthesizing a diverse group of bioactive metabolites known as alkylamides. Optimum regeneration frequency (90.5%) with desirable multiple shoot buds was observed without inter-vening callus phase from nodal explants in Murashige and Skoog's (MS) medium supplemented with 0.5 mg l-1 each of BAP (6-benzylaminopurine) and IBA (indole-3-butyric acid). Organogenic callus was induced on MS medium containing 2, 4-D (2, 4-dichlorophenoxyacetic acid), Kn (Kinetin) and BAP (1.0 + 0.5 + 0.5 mg l-1), respectively from secondary axenic leaf explants. The survival rate of rooted plantlets transferred to sand: soil (1:1; v/v) after hardening procedures was 90%. Variation in spilanthol quantity among 42 regener-ated plants was determined by high-performance liquid chromatography and one plant designated (SA-31) showed significantly higher accumulation of spilanthol (0.05%) as compared to the donor mother (0.02%) plant on dry weight (DW). Genetic fidelity between the regenerated plants and the mother plant was assessed by RAPD (random amplification of Polymorphic DNA) analysis. A comparative analysis revealed that leaves of regenerated plants through indirect organogenesis exhibited high antioxidant activities with total flavonoids (4.03 +/- 0.49 mg/g), total phenolics (4.68 +/- 0.49 mg/g) and a, a-diphenyl-b-picrylhydrazyl radical scavenging activity (IC50 value of 166.21 +/- 24.45) DW than the field grown plants. This study demonstrated an efficient, high frequency in vitro regeneration protocol that induced chemotypic variability for the devel-opment of high yielding clones for pharmaceutical purposes.(c) 2022 SAAB. Published by Elsevier B.V. All rights reserved.