Does synthetic seed storage at higher temperature reduce reserpine content of Rauvolfia serpentina (L.) Benth. ex Kurz.?

Developments in biotechnological tools and techniques for production of reserpine

In the quest for novel medications, researchers have kept on studying nature to unearth beneficial plant species with medicinal qualities that may cure various diseases and disorders. These medicinal plants produce different bioactive secondary metabolites with immense therapeutic importance. One such valuable secondary metabolite, reserpine (C₃₃H₄₀N₂O₉), has been used for centuries to cure various ailments like hypertension, cardiovascular diseases, neurological diseases, breast cancer, and human promyelocytic leukaemia. Rauvolfia spp. (family Apocynaceae) is an essential reservoir of this reserpine. The current review thoroughly covers different non-conventional or in vitro-mediated biotechnological methods adopted for pilot-scale as well as large-scale production of reserpine from Rauvolfia spp., including techniques like multiple shoot culture, callus culture, cell suspension culture, precursor feeding, elicitation, synthetic seed production, scale-up via bioreactor, and hairy root culture. This review further analyses the unexplored and cutting-edge biotechnological tools and techniques to alleviate reserpine production. KEY POINTS: • Reserpine, a vital indole alkaloid from Rauvolfia spp., has been used for centuries to cure several ailments. • Overview of biosynthetic pathways and biotechnological applications for enhanced production of reserpine. • Probes the research gaps and proposes novel alternative techniques to meet the pharmaceutical industry's need for reserpine while reducing the over-exploitation of natural resources.

Biotechnological interventions and indole alkaloid production in Rauvolfia serpentina

Rauvolfia serpentina (L). Benth. ex Kurz. (Apocynaceae), commonly known as Sarpagandha or Indian snakeroot, has long been used in the traditional treatment of snakebites, hypertension, and mental illness. The plant is known to produce an array of indole alkaloids such as reserpine, ajmaline, amalicine, etc. which show immense pharmacological and biomedical significance. However, owing to its poor seed viability, lesser germination rate and overexploitation for several decades for its commercially important bioactive constituents, the plant has become endangered in its natural habitat. The present review comprehensively encompasses the various biotechnological tools employed in this endangered Ayurvedic plant for its in vitro propagation, role of plant growth regulators and additives in direct and indirect regeneration, somatic embryogenesis and synthetic seed production, secondary metabolite production in vitro, and assessment of clonal fidelity using molecular markers and genetic transformation. In addition, elicitation and other methods of optimization of its indole-alkaloids are also described herewith. KEY POINTS: • Latest literature on in vitro propagation of Rauvolfia serpentina • Biotechnological production and optimization of indole alkaloids • Clonal fidelity and transgenic studies in R. serpentina.

Ameliorated reserpine production via in vitro direct and indirect regeneration system in Rauvolfia serpentina (L.) Benth. ex Kurz

Rauvolfia serpentina (L.) Benth. ex Kurz., popularly known as Indian Snakeroot plant, belonging to Apocynaceae family, holds immense medicinal importance, owing to its rich source of multiple secondary metabolites such as ajmaline, ajmalicine, reserpine, and serpentine. To meet the constant demands for the key secondary metabolite (reserpine) by majority of the pharmaceutical industries, the present study assessed the effects of direct and indirect regeneration system on amelioration of reserpine accumulation in shoots of R. serpentina. In vitro multiple shoot cultures were established using shoot tip explants. Best results for shoot initiation, multiplication, and biomass production were obtained in case of Murashige and Skoog medium, supplemented with 1 mg/l N⁶-benzyladenine. The multiple shoots were then sub-cultured on cytokinin–auxin combination media for further proliferation. Highest shoot and leaf multiplication rates and the most enhanced biomass were obtained in case of 1–1.5 mg/l Kinetin + 0.2 mg/l α-naphthalene acetic acid (NAA). Callus induction and its subsequent proliferation was obtained using 1.5 mg/l 2,4-dichlorophenoxyacetic acid. The best indirect shoot regeneration with highest shoot and leaf proliferation from calli was observed in case of 1 mg/l thidiazuron + 0.2 mg/l NAA. Reserpine content estimation via HPTLC from in vitro shoots (direct regeneration) and calli (indirect regeneration) were recorded to undergo an almost three-fold and two-fold increment (respectively) in comparison to that of the mother plant. Thus, in vitro direct regeneration system proved to be more effective and efficient in ameliorating the reserpine content.

Biotechnological interventions on the genus Rauvolfia: recent trends and imminent prospects

Rauvolfia spp., also known as devil peppers, are a group of evergreen shrubs and trees. Among the ~ 76 various species, Rauvolfia serpentina is the most important one as it finds its use as an important medicinal plant. It is commonly known as the Indian snakeroot plant or Sarpagandha. The plant is rich in multiple secondary metabolites. Some of the well-known secondary metabolites are reserpine, ajmaline, ajmalicine, serpentine, yohimbine, etc. Alkaloids are also found in all parts of the plant but the richest sources are the roots. Since ancient times, roots (mainly due to reserpine) have been utilized in various Ayurvedic and Unani medicinal preparations for the treatment of diseases like hypertension, anxiety, insomnia and schizophrenia. Apart from this, there are many other pharmacological and ethnobotanical uses of this plant. There are a number of published reports regarding tissue culture techniques on Rauvolfia spp. The current review mainly illustrates and discusses the various in vitro biotechnological aspects such as direct regeneration, indirect regeneration via callus formation, somatic embryogenesis, synthetic seed production, hairy root culture, polyploidy induction and secondary metabolite estimation, which provides significant ideas regarding the ongoing research activities and future prospects related to the genetic improvement of this genus.