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

• Spilanthes acmella is used in beauty care for accelerating the muscle relaxant and for repairing functional wrinkles. • It is the only report describing high-frequency shoot regeneration protocol. • The regenerated plants performed well under field conditions after hardening. • RAPD were used for the determination of genetic variability. • Chemotype with high spilanthol content (somoclone) was obtained from the current study. 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 intervening 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 regenerated 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 α, α-diphenyl-β-picrylhydrazyl radical scavenging activity (IC 50 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 development of high yielding clones for pharmaceutical purposes. [ABSTRACT FROM AUTHOR]