De novo transcriptome based insights into secondary metabolite biosynthesis in Malaxis acuminata (Jeevak)-A therapeutically important orchid.

Malaxis acuminata D. Don [=Crepidium acuminatum (D. Don) Szlach.] is an endangered medicinal orchid of the Ashtvarga group of plants in Ayurveda (Indian system of traditional medicine). Using a combination of aromatic cytokinin [meta-Topolin (mT)], plant biostimulant (chitosan), auxin [indole-3-butyric acid (IBA)], and a phenolic elicitor [phloroglucinol (PG)], plants of M. acuminata were regenerated in vitro for mass multiplication. The present research reveals the first-ever transcriptome of M. acuminata. A total of 43,111 transcripts encoding 23,951 unigenes were assembled de novo from a total of 815.02 million reads obtained from leaf and pseudobulb of in vitro raised M. acuminata. Expression analysis of genes associated with ß-sitosterol and eugenol biosynthesis in leaf and pseudobulb provided vital clues for differential accumulation of metabolites in M. acuminata. Ultra-performance liquid chromatography (UPLC) confirmed higher amounts of ß-sitosterol and eugenol content in the leaf as compared to the pseudobulb. Differential expression of transcripts related to starch and sucrose metabolism, plant hormone signal transduction, diterpenoid biosynthesis, phenylalanine metabolism, stilbenoid, diarylheptanoid, and gingerol biosynthesis suggested the operation of differential metabolic pathways in leaf and pseudobulb. The present research provides valuable information on the biosynthesis of secondary metabolites in M. acuminata, which could be used for advanced metabolite bioprospection using cell suspension culture and bioreactor-based approaches. Data also suggested that leaf tissues rather than pseudobulb can be used as an alternate source of bioactive metabolites thereby shifting the need for harvesting the pseudobulb. This will further facilitate the conservation and sustainable utilization of this highly valued medicinal orchid.

Indirect organogenesis-mediated high frequency conversion of non-embryonic synthetic seeds, essential oil profiling and antibacterial activity in genetically stable plants of Patchouli.

Patchouli is a prized tropical medicinal herb with broad-spectrum therapeutic importance. The present research work describes development of an efficient callus-mediated plant regeneration protocol along with associated germplasm portability system (via alginate-encapsulation). Using 1.5 mg/l α-naphthalene acetic acid (NAA) and 1.0 mg/l 2, 4-dichlorophenoxy acetic acid (2, 4-D), highly proliferative friable calli were produced that subsequently underwent organogenesis in combinatorial cytokinin treatment to yield multiple shoot clusters. The highest frequency of shoot formation was achieved using 1.5 mg/l NAA with 1.5 mg/l 6-benzylaminopurine (BAP) in Murashige and Skoog (MS) medium. In vitro-derived shoot tips were encapsulated with 3% sodium alginate and 100 mM CaCl2 solution. The encapsulated beads were germinated in MS media with various concentrations of polyamines, where the highest regeneration frequency was observed with 1.5 mg/l spermidine. The regenerated shoots were rooted in basal MS medium and were successfully acclimatized with 96% survival rate. Genetic homogeneity amongst the regenerated plantlets was validated using Start Codon Targeted polymorphism (SCoT) and CAAT box-derived polymorphism (CBDP) ascertaining a high degree of clonal fidelity. The essential oil (EO) profiling of the donor plant and the in vitro-derived plantlets revealed identical composition. Furthermore, the antibacterial activities of various tissue extracts and extracted EOs were evaluated against the opportunistic pathogens viz. Klebsiella pneumoniae (MTCC 109), Salmonella typhii (MTCC 733), Micrococcus luteus (MTCC 2470) and Staphylococcus aureus (MTCC 96). The minimum inhibitory concentration (MIC) ranged from 0.31 to 5.0 mg/ml and 2.5 to 5.0 mg/ml against Gram-positive and Gram-negative bacteria, respectively. Eventually, the present research provides a holistic insight into the rapid regeneration of quality planting material as well as pharmacological bioprospection of patchouli along with the scope of further qualitative improvement via genetic transformation. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03302-3.

Chemical Composition and Cytotoxic Activity of the Essential Oil and Oleoresins of In Vitro Micropropagated Ansellia africana Lindl: A Vulnerable Medicinal Orchid of Africa.

Orchids are rich treasure troves of various important phytomolecules. Among the various medicinal orchids, Ansellia africana stands out prominently in the preparing of various herbal medicines due to its high therapeutic importance. The nodal explants of A. africana were sampled from asymbiotically germinated seedlings on basal Murashige and Skoog (MS) medium and were micropropagated in MS medium supplemented with 3% sucrose and 10 µM meta topolin (mT) + 5 µM naphthalene acetic acid (NAA) +15 µM indole butyric acid (IBA) + 30 µM phloroglucinol (PG). In the present study, the essential oil was extracted by hydrodistillation and the oleoresins by the solvent extraction method from the micropropagated A. africana. The essential oil and the oleoresins were analysed by Gas Chromatography (GC) and GC/MS (Mass spectrometry). A total of 84 compounds were identified. The most predominant components among them were linoleic acid (18.42%), l-ascorbyl 2,6-dipalmitate (11.50%), linolenic acid (10.98%) and p-cresol (9.99%) in the essential oil; and eicosane (26.34%), n-butyl acetate (21.13%), heptadecane (16.48%) and 2-pentanone, 4-hydroxy-4-methyl (11.13%) were detected in the acetone extract; heptadecane (9.40%), heneicosane (9.45%), eicosane (6.40%), n-butyl acetate (14.34%) and styrene (22.20%) were identified and quantified in the ethyl acetate extract. The cytotoxic activity of essential oil and oleoresins of micropropagated A. africana was evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide) assay on Vero cells compared to the standard drug doxorubicin chloride. The present research contains primary information about the therapeutic utility of the essential oil and oleoresins of A. africana with a promising future research potential of qualitative and quantitative improvement through synchronised use of biotechnological techniques.

Applicability of ISSR and DAMD markers for phyto-molecular characterization and association with some important biochemical traits of Dendrobium nobile, an endangered medicinal orchid.

Dendrobium nobile is an important medicinal orchid having profound importance in traditional herbal drug preparations and pharmacopeias worldwide. Due to various anthropogenic pressures the natural populations of this important orchid species are presently facing threats of extinction. In the present study, genetic and chemical diversity existing amongst 6 natural populations of D. nobile were assessed using molecular markers, and the influence of genetic factors on its phytochemical activity especially antioxidant potential was determined. Molecular fingerprinting of the orchid taxa was performed using ISSR and DAMD markers along with the estimation of total phenolics, flavonoids and alkaloid contents. Antioxidant activity was also measured using DPPH and FRAP assays which cumulatively revealed a significant level of variability across the sampled populations. The representatives from Sikkim in Northeast India revealed higher phytochemical activity whereas those from Mizoram showed lesser activity. Analysis of molecular variance (AMOVA) revealed that variation amongst the populations was significantly higher than within the populations. The data generated by UPGMA and Bayesian analytical models were compared in order to estimate the genetic relationships amongst the D. nobile germplasm sampled from different geographical areas of Northeast India. Interestingly, identical grouping patterns were exhibited by both the approaches. The results of the present study detected a high degree of existing genetic and phytochemical variation amongst the populations in relation to bioclimatic and geographic locations of populations. Our results strongly establish that the cumulative marker approach could be the best suited for assessing the genetic relationships with high accuracy amongst distinct D. nobile accessions.