Laxminarain Misra

Withaferin A induces apoptosis by activating p38 mitogen-activated protein kinase signaling cascade in leukemic cells of lymphoid and myeloid origin through mitochondrial death cascade

Withaferin A (WA) is present abundantly in Withania somnifera, a well-known Indian medicinal plant. Here we demonstrate how WA exhibits a strong growth-inhibitory effect on several human leukemic cell lines and on primary cells from patients with lymphoblastic and myeloid leukemia in a dose-dependent manner, showing no toxicity on normal human lymphocytes and primitive hematopoietic progenitor cells. WA-mediated decrease in cell viability was observed through apoptosis as demonstrated by externalization of phosphatidylserine, a time-dependent increase in Bax/Bcl-2 ratio; loss of mitochondrial transmembrane potential, cytochrome c release, caspases 9 and 3 activation; and accumulation of cells in sub-G0 region based on DNA fragmentation. A search for the downstream pathway further reveals that WA-induced apoptosis was mediated by an increase in phosphorylated p38MAPK expression, which further activated downstream signaling by phosphorylating ATF-2 and HSP27 in leukemic cells. The RNA interference of p38MAPK protected these cells from WA-induced apoptosis. The RNAi knockdown of p38MAPK inhibited active phosphorylation of p38MAPK, Bax expression, activation of caspase 3 and increase in Annexin V positivity. Altogether, these findings suggest that p38MAPK in leukemic cells promotes WA-induced apoptosis. WA caused increased levels of Bax in response to MAPK signaling, which resulted in the initiation of mitochondrial death cascade, and therefore it holds promise as a new, alternative, inexpensive chemotherapeutic agent for the treatment of patients with leukemia of both lymphoid and myeloid origin.

Withanolide A is inherently de novo biosynthesized in roots of the medicinal plant Ashwagandha (Withania somnifera).

Ashwagandha (Withania somnifera Dunal., Solanaceae) is one of the most reputed medicinal plants of Ayurveda, the traditional medical system. Several of its traditionally proclaimed medicinal properties have been corroborated by recent molecular pharmacological investigations and have been shown to be associated with its specific secondary metabolites known as withanolides, the novel group of ergostane skeletal phytosteroids named after the plant. Withanolides are structurally distinct from tropane/nortropane alkaloids (usually found in Solanaceae plants) and are produced only by a few genera within Solanaceae. W. somnifera contains many structurally diverse withanolides in its leaves as well as roots. To date, there has been little biosynthetic or metabolism-related research on withanolides. It is thought that withanolides are synthesized in leaves and transported to roots like the tropane alkaloids, a group of bioactive secondary metabolites in Solanaceae members known to be synthesized in roots and transported to leaves for storage. To examine this, we have studied incorporation of (14)C from [2-(14)C]-acetate and [U-(14)C]-glucose into withanolide A in the in vitro cultured normal roots as well as native/orphan roots of W. somnifera. Analysis of products by thin layer chromatography revealed that these primary metabolites were incorporated into withanolide A, demonstrating that root-contained withanolide A is de novo synthesized within roots from primary isoprenogenic precursors. Therefore, withanolides are synthesized in different parts of the plant (through operation of the complete metabolic pathway) rather than imported.

Withanolide biosynthesis recruits both mevalonate and DOXP pathways of isoprenogenesis in Ashwagandha Withania somnifera L. (Dunal)

AbstractWithanolides are pharmaceutically important C28-phytochemicals produced in most prodigal amounts and diversified forms by Withania somnifera. Metabolic origin of withanolides from triterpenoid pathway intermediates implies that isoprenogenesis could significantly govern withanolide production. In plants, isoprenogenesis occurs via two routes: mevalonate (MVA) pathway in cytosol and non-mevalonate or DOXP/MEP pathway in plastids. We have investigated relative carbon contribution of MVA and DOXP pathways to withanolide biosynthesis in W. somnifera. The quantitative NMR-based biosynthetic study involved tracing of 13C label from 13C1-d-glucose to withaferin A in withanolide producing in vitro microshoot cultures of the plant. Enrichment of 13C abundance at each carbon of withaferin A from 13C1-glucose-fed cultures was monitored by normalization and integration of NMR signal intensities. The pattern of carbon position-specific 13C enrichment of withaferin A was analyzed by a retro-biosynthetic approach using a squalene-intermediated metabolic model of withanolide (withaferin A) biosynthesis. The pattern suggested that both DOXP and MVA pathways of isoprenogenesis were significantly involved in withanolide biosynthesis with their relative contribution on the ratio of 25:75, respectively. The results have been discussed in a new conceptual line of biosynthetic load-driven model of relative recruitment of DOXP and MVA pathways for biosynthesis of isoprenoids. Key message The study elucidates significant contribution of DOXP pathway to withanolide biosynthesis. A new connotation of biosynthetic load-based role of DOXP/MVA recruitment in isoprenoid biosynthesis has been proposed.

Selective reactivity of 2-mercaptoethanol with 5β,6β-epoxide in steroids from Withania somnifera

Abstract 2-Mercaptoethanol reacts selectively with the 5β,6β-epoxy steroids isolated from Withania somnifera substituting the epoxide by a six-membered oxyethylene-2′-thio ring whereas it failed to show such reactivity on 6α,7α-epoxy withasteroids. The structure of the product has been elucidated by spectroscopic methods, especially applying extensive 2D NMR methods. The anticancer activity of withaferin A was lost in the reaction product indicating that its activity is also linked to the free 5β,6β-epoxide functional group.

New Withanolides from Fresh Berries of Withania somnifera

Abstract The chloroform extract of the fresh berries of Withania somnifera has been investigated to afford stigmasterol, its glucoside, withanone, 27-hydroxy withanolide A along with two new withanolides, namely, iso-withanone (1) and 6α,7α-epoxy-1α,3β ,5α-trihydroxy-witha-24-enolide (2). Compound 1 possesses an uncommon 17α-oriented side chain whereas compound 2 has 1α,3β - dihydroxy group which is a molecule of biogenetic significance for withasteroids.

Triterpenoids, essential oil and photo-oxidative 28->13-lactonization of oleanolic acid from Lantana camara.

Two novel triterpenoids have been isolated from the roots of Lantana camara L.: 3beta,19alpha dihydroxy ursan-28-oic acid and 21,22beta-epoxy-3beta-hydroxy olean-12-en-28-oic acid in its methyl ester form. Its leaves have yielded an essential oil which is rich in sesquiterpenes. Oleanolic acid, which is thought to be a hepatoprotective compound, was isolated from L. camara roots and converted into its 28 --> 13beta lactone by a facile photo-oxidation reaction.

Antibacterial, cytotoxic activities and chemical composition of fruits of two Cameroonian Zanthoxylum species

ETHNOPHARMACOLOGICAL RELEVANCE Zanthoxylum leprieurii (Syn. Fagara leprieurii) is a plant extensively used by traditional healers in Cameroon for the treatment of stomach disorders, gonorrhea, intestinal parasites and sterility. The infusion from the fruit is taken in Cameroon for the treatment of sickle cell anemia, as well. Similarly, the roots of Zanthoxylum zanthoxyloides (Syn. Fagara zanthoxyloides) are also used for wound dressing, sickle cell anemia and as pain reliever, in addition to the uses mentioned for Zanthoxylum leprieurii. AIM OF THE STUDY To scientifically validate their traditional use, the in vitro antimicrobial and anticancer assays were performed. In addition, chemical compositions of their fruit extracts and essential oils were also studied. MATERIAL AND METHODS The chemical compositions of their essential oils and methanol extracts were studied. GC and GC-MS were used for analyzing the essential oils while various chromatographic methods were used to isolate the pure compounds from methanol extracts. MTT assay was used for the cytotoxic studies of methanol extracts, their fractions and some pure compounds. Antimicrobial activity of methanol extracts, some isolated compounds as well as essential oils was tested against a panel of human pathogenic bacteria by diffusion and dilution methods. RESULTS The principal constituents of the essential oil of Zanthoxylum zanthoxyloides were identified as citronellol and geraniol whereas Zanthoxylum leprieurii was rich in E-β-ocimene. Furthermore, we report for the first time, the presence of 7,8-dimethoxycoumarin and sinapic acid in the methanol extract of Zanthoxylum leprieurii. In vitro bioassays reveal that the methanol extracts, essential oil and some of the isolated compounds from fruits of both the plants exhibit moderate anticancer and antimicrobial activities. CONCLUSION Altogether, the present findings justify the traditional use of Zanthoxylum zanthoxyloides and Zanthoxylum leprieurii in the treatment of stomach disorders and cancer disease. The antimicrobial properties in the essential oil of Zanthoxylum zanthoxyloides are of additional significance.

Tropine Forming Tropinone Reductase Gene from Withania somnifera (Ashwagandha): Biochemical Characteristics of the Recombinant Enzyme and Novel Physiological Overtones of Tissue-Wide Gene Expression Patterns

Withania somnifera is one of the most reputed medicinal plants of Indian systems of medicine synthesizing diverse types of secondary metabolites such as withanolides, alkaloids, withanamides etc. Present study comprises cloning and E. coli over-expression of a tropinone reductase gene (WsTR-I) from W. somnifera, and elucidation of biochemical characteristics and physiological role of tropinone reductase enzyme in tropane alkaloid biosynthesis in aerial tissues of the plant. The recombinant enzyme was demonstrated to catalyze NADPH-dependent tropinone to tropine conversion step in tropane metabolism, through TLC, GC and GC-MS-MS analyses of the reaction product. The functionally active homodimeric ∼60 kDa enzyme catalyzed the reaction in reversible manner at optimum pH 6.7. Catalytic kinetics of the enzyme favoured its forward reaction (tropine formation). Comparative 3-D models of landscape of the enzyme active site contours and tropinone binding site were also developed. Tissue-wide and ontogenic stage-wise assessment of WsTR-I transcript levels revealed constitutive expression of the gene with relatively lower abundance in berries and young leaves. The tissue profiles of WsTR-I expression matched those of tropine levels. The data suggest that, in W. somnifera, aerial tissues as well possess tropane alkaloid biosynthetic competence. In vivo feeding of U-[14C]-sucrose to orphan shoot (twigs) and [14C]-chasing revealed substantial radiolabel incorporation in tropinone and tropine, confirming the de novo synthesizing ability of the aerial tissues. This inherent independent ability heralds a conceptual novelty in the backdrop of classical view that these tissues acquire the alkaloids through transportation from roots rather than synthesis. The TR-I gene expression was found to be up-regulated on exposure to signal molecules (methyl jasmonate and salicylic acid) and on mechanical injury. The enzymes catalytic and structural properties as well as gene expression profiles are discussed with respect to their physiological overtones.

Epoxide group relationship with cytotoxicity in withanolide derivatives from Withania somnifera.

Withania somnifera is one of the highly reputed medicinal plants of India. Its steroidal constituents exist in the form of two major substitution patterns, viz. withaferin A (1) and withanone (5). Withaferin A with oxidation at carbons 4, 5, and 6 is considered as an active type, especially as anticancer, whereas the withanones with oxidation at carbons 5, 6, and 7 rarely show any activity. We prepared a series of derivatives with modifications at carbons 5, 6, and 7 in ring B of these withanolides to study the role of the epoxide group towards the cytotoxic property of these bioactive steroids. We have converted withanolides into the respective thiiranes, amino alcohols and alcohols by selective reactions at the epoxide ring and were evaluated for in vitro anticancer activity against four cancer cell lines to study the structure activity relationships. The transformations of the epoxide group in withanolides of the withaferin A type showed moderate reduction in their cytotoxicity whereas the almost inactive withanones have shown some improvements in their alcohol derivatives.

Carotane derivatives from Ferula jaeschkeana

Abstract The petrol extract of Ferula jaeschkeana rhizomes afforded, in addition to jaeschkeanadiol, 5α-(4-hydroxybenzoyl)-jaeschkeanadiol, and 5α-(3-methoxy-4-hydroxybenzoyl)-jaeschkeanadiol, a new carotane derivative having a γ-lactone moiety. The structures were elucidated by spectroscopic studies.