Genetic stability and phytochemical analysis of the in vitro regenerated plants of Dendrobium nobile Lindl., an endangered medicinal orchid

In vitro inhibitory effects on free radicals, pigmentation, and skin cancer cell proliferation from Dendrobium hybrid extract: A new plant source of active compounds

Orchidaceae are diverse plants whose bioactive compounds have various biological activities. New hybrids of Dendrobium have been generated to gain characteristics shared with their ancestors. Dendrobium Pearl Vera (designated as DH) is derived from parents used for dermatological treatments and cosmetics. However, the phytoconstituents and biological properties of DH have not been reported. The current study investigated extracts from DH plants using four solvents (water, methanol, ethanol, or 2-propanol). The propanolic extract (DH-P) contained the highest phenolic and flavonoid contents, along with a high scavenging performance for free radicals. In total, 25 tentative constituents in the DH-P matrix were identified, consisting of amino acids, nucleotides, and three types of secondary metabolites: furan, phenolics, and alkaloids. The DH-P inhibited human tyrosinase in vitro in a concentration-dependent manner of the phenolic content. Furthermore, there was no significant difference between DH-P with 10 μg/ml phenolic content and 0.75 mM kojic acid (a commercial whitening agent) on the inhibition of human tyrosinase. Incubation with DH-P containing at least 15 μg/ml phenolic content greatly inhibited the proliferation of human melanoma; however, the cell viability was not affected by the phenolic content at 5 μg/ml or less. The half-maximal inhibitory concentration (IC50) of the phenolic content in DH-P on melanoma viability was 12.90 ± 1.04 μg/ml. Melanin production in vivo by human melanoma incubated with 5 μg/ml phenolic content in DH-P was reduced significantly, compared to 2.5 μg/ml phenolic content in DH-P, 100 μg/ml arbutin, and in control. The identified components, including 5-hydroxymethyl-2-furaldehyde, salicylic acid, nicotinamide, acetophenone, cytidine, adenosine, proline, or valine, have been reported to be associated with depigmentation, antioxidant, and anticancer. This research revealed, for the first time, the tentative phytoconstituents of Dendrobium Pearl Vera and their biological activities, thus demonstrating the potential use of DH-P in dermal applications.

Genome-wide identification and analysis of the PAL genes from the orchids Apostasia shenzhenica, Dendrobium catenatum and Phalaenopsis equestris

Phenylalanine ammonia-lyase (PAL) is a key gateway enzyme that connects the phenylpropanoid pathway to primary metabolism. The phenylpropanoid pathway plays a vital role in the growth and environmental adaptation of many plants leading to the production of valuable bioactive compounds with industrial and medical applications. In the present study, nine putative PAL genes from three orchids were identified; five in Apostasia shenzhenica and two each in Dendrobium catenatum and Phalaenopsis equestris. Eighteen motifs and four major conserved functional domains were identified as reported in PAL proteins of other species. All the nine PALs were stable based on their computed physicochemical properties and localized in the cytoplasm. The three-dimensional structures of PALs revealed a homo-tetrameric structure consisting of four identical subunits. A total of 21 cis-regulatory elements with known functions were identified from the promoter regions of all PALs which are responsible for various plant responses to light, stress and growth regulators like auxins, gibberellins and abscisic acid. Phylogenetic analysis showed that the studied PAL proteins clustered in two major clades (clade I and II), placing dicot and monocot PALs in two separate monophyletic clades. In silico gene expression of the identified PALs in different vegetative and reproductive tissues revealed the differential expressions based on tissue type and disclosed that the expression of PAL genes was upregulated in all the tissues examined with an exception of PePAL leaf samples where no expression was detected, however, the same being highly expressed in reproductive tissues (PePAL1-labellum; PePAL2-sepal). In case of AsPALs, the expression was found to be highest in reproductive tissues (AsPAL4-maximum in inflorescence). On the other hand, the expression of DcPALs was found to be highest in vegetative tissues (DcPAL2-maximum in root). Based on the medicinal importance of orchids and the significant role of PAL genes in synthesis of bioactive compounds, the functional characterization of PAL genes can be further exploited in genetic improvement of medicinal orchids.Communicated by Ramaswamy H. Sarma.

Xylochemical Synthesis and Biological Evaluation of the Orchidaceous Natural Products Isoarundinin I, Bleochrin F, Blestanol K, and Pleionol

The first total syntheses of the orchid-derived natural products isoarundinin I (1), (±)-bleochrin F ((±)-2), (±)-blestanol K ((±)-3), and (±)-pleionol ((±)-4) from renewable starting materials are reported, along with the evaluation of their biological activities. The total syntheses were based on regioselective aromatic bromination reactions in combination with a key acid-promoted regioselective intramolecular cyclization. The biological results suggest that isoarundinin I (1), (±)-blestanol K ((±)-3), and (±)-pleionol ((±)-4) have the potential to inhibit the growth of both sensitive and multidrug-resistant cancer cells.

Micropropagation and assessment of genetic stability of Dendrobium transparens Wall. Ex Lindl. using RAPD and ISSR markers

Introduction

Dendrobium species have been widely used for many health disorders since ancient times. However, due to unrelenting collection to meet the increasing demand for their use in medication and other health products, the natural habitats of medicinal Dendrobium transparens have been devastated and are on the verge of extinction.

Methods

An efficient in-vitro propagation protocol for Dendrobium transparens using seed derived protocorms was established and genetic homogeneity of the in-vitro regenerants and the wild plant was studied.

Results

The maximum seed germination was observed in Full strength Murashige and Skoog medium (FMS). Induction of protocorms were achieved on basal as well as half-strength MS medium. The highest number of shoot (11.9 shoots/explant) was achieved in half MS medium fortified with 100 mL/L coconut water in addition with Benzyl amino purine (BAP) 1 mg/L and Kinetin 2 mg/L. Further, elongated shoots were transferred to full and half strength MS root initiating medium supplemented with different concentration of auxins. However, a maximum of (8.3 ± 0.6, 4.9 ± 0.1 cm) roots were achieved in full MS medium fortified with 100 mL/L coconut water and Napthalene acetic acid (NAA) 1.5 mg/L. Ten rapid Random Amplified Polymorphic DNA (RAPD) and Inter Simple Sequence Repeats (ISSR) primers were used to analyze genetic stability among in-vitro and mother plant. RAPD primers produced a total of 23 fragments while ISSR primers produced a total of 16 fragments.

Conclusion

The amplified bands of all the samples of in-vitro plants were similar to bands of mother plant. The present research reported here is indicating the applicability of tissue culture for true-to-type plant production and conservation of D. transperens.

The Transcriptome Profiling of Flavonoids and Bibenzyls Reveals Medicinal Importance of Rare Orchid Arundina graminifolia

Orchids are very important flowering plants that spend long juvenile phases before flowering. Along with aesthetic importance, they are rich sources of medicinal components. However, their long reproductive cycle is the major hurdle to study the medicinal efficacy. Arundina graminifolia is a rare orchid that grows fast, unlike other orchids, and this characteristic makes it an ideal plant to study the medicinal enrichment of orchids. Therefore, this study presents the identification of important medicinal components in various parts of A. graminifolia. Transcriptome analysis was performed for five stages (FD1-FD5) of flower development and four tissue types (mature flower, silique, root, and leaf) to ascertain genetic regulators of flavonoids and bibenzyls. Most of the genes showed the highest expression in roots as compared with other tissues. Weighted gene coexpression network analysis (WGCNA) was performed to identify the coexpression modules and the candidate genes involving biosynthesis pathways of these chemicals. MEyellow module contained the highly coexpressed genes. Moreover, the concentrations of phenylpropanoid, bibenzyls, and flavone were ascertained through high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Phenylpropanoid and bibenzyl were comparatively high in the leaf, while flavone showed a high concentration in the stem. The selected candidate genes [bibenzyl biosynthesis (BIBSY212), CYP84A1, CYP73A4, 4CLL7, UGT88B1, UGT73C3, anthocyanin synthase (ANS), phenylalanine ammonia-lyase (PAL), flavanone synthase FLS, and CHS8] were validated through quantitative real-time PCR (qRT-PCR). Most of these genes showed high expression in leaf and root as compared with other tissue. Therefore, the presence of bibenzyls and flavonoids in different parts of A. graminifolia and their molecular regulators can provide a quick source to decipher the medicinal efficacy of orchids.

Identification of SCAR markers for genetic authentication of Dendrobium nobile Lindl

Dendrobium nobile Lindl. is an orcid plant with important medicinal values. This is a colourful houseplant, and also a popular herb in traditional Chinese medicine (TCM). The variants of this plant from different geographic regions might be high, and in this study, we aimed to develop specific sequence characterized amplified region (SCAR) markers for the identification of specific variant of this plant. Different cultivars of D. nobile were collected from nine different places of China, and one cultivar from Myanmar. DNA materials were extracted from the plant samples, random amplified polymorphic DNA (RAPD) were developed, cloned and sequenced for the development of SCAR markers. We have developed four SCAR markers, which are specific to the cultivar from Luzhou China, and clearly distinguishable (genetically) from other cultivars. These SCAR markers are deposited in GenBank (accession number MZ417502, MZ484089, MZ417504 and MZ417505). Four SCAR markers for D. nobile are effective molecular technique to genetically identify the different cultivars or species, and this method is applicable for genetic characterization and identification of other plant species too.

In Vitro Florigenesis with Special Reference to Orchids- A Review

BACKGROUND

Orchids are widely used in floriculture as attractive cut flowers all over the world. The current paper reviews factors affecting the in vitro flowering in orchid species.

METHODS

The phenomenon of in vitro flowering is advantageous as it shortens the breeding cycle, which is prolonged in the in vivo grown orchid species of commercial value. Certain genetic and biochemical mechanisms are involved at the time of onset of flowering in orchid plants. In the present endeavour, efforts have been made to initiate in vitro flowering in terrestrial and epiphytic orchid species. Various phenomenon involved during transition of vegetative shoot apex into floral axis is also reviewed.

RESULTS

In vitro flowering was induced in Dendrobium nobile and Zeuxine strateumatica in Mitra medium supplemented with BAP at 0.5 in mgl^-1.

CONCLUSION

In vitro flowering can be initiated by manipulating physical and chemical stimulus in the nutrient regime. The study would be helpful in better understanding the complex process of flowering in vitro as well as ex vitro.

Virtual screening of natural compounds for potential inhibitors of Sterol C-24 methyltransferase of Leishmania donovani to overcome leishmaniasis

Leishmaniasis is a neglected tropical disease caused by trypanosomatid parasite belonging to the genera Leishmania. Leishmaniasis is transmitted from one human to other through the bite of sandflies. It is endemic in around 98 countries including tropical and subtropical regions of Asia, Africa, Southern America, and the Mediterranean region. Sterol C-24 methyltransferase (LdSMT) of Leishmania donovani (L. donovani) mediates the transfer of CH3-group from S-adenosyl methionine to C-24 position of sterol side chain which makes the ergosterol different from cholesterol. Absence of ortholog in human made it potential druggable target. Here, we performed virtual screening of library of natural compounds against LdSMT to identify the potential inhibitor for it and to fight leishmaniasis. Gigantol, flavan-3-ol, and parthenolide showed the best binding affinity towards LdSMT. Further, based on absorption, distribution, metabolism, and excretion properties and biological activity prediction, gigantol showed the best lead-likeness and drug-likeness properties. Therefore, we further elucidated its antileishmanial properties. We found that gigantol inhibited the growth and proliferation of promastigotes as well as intra-macrophagic amastigotes. Gigantol exerted its antileishmanial action through the induction of reactive oxygen species in dose-dependent manner. Our study, suggested the possible use of gigantol as antileishmanial drug after further validations to overcome leishmaniasis.

RAPD, ISSR, and SCoT markers based genetic stability assessment of micropropagated Dendrobium fimbriatum Lindl. var. oculatum Hk. f.- an important endangered orchid

Dendrobium fimbriatum is an ornamental and medicinal orchid listed in the Red data book of IUCN. Phytohormones' effect on the in vitro regeneration of the orchid was studied using Mitra medium supplemented with different growth regulators. KN produced effective shoot formation when present alone or in combination with IBA or NAA. The shooting was gradually increased when KN concentration was increased from 0.8 to 4.8 mg L^-1, but the opposite response was observed with BAP at higher concentration (4.8 mg L^-1). IBA either in combination with BAP or KN promoted effective root development and multiplication. Micropropagated orchids grown in the basal medium devoid of any phytohormone showed 100% monomorphism, while low genetic polymorphism of 1.52% (RAPD-Random Amplification of Polymorphic DNA), 1.19% (ISSR-Inter Simple Sequence Repeat) and 3.97% (SCoT-Start Codon Targeted) was exhibited among the regenerants propagated in the hormone enriched medium. UPGMA (Unweighted pair group method using arithmetic averages) dendrograms showed the grouping of mother plant (MP) with the in vitro regenerants. The principal coordinate analysis (PCoA) further confirmed the clustering patterns as determined by the cluster analysis. The study reported for the first time the successful in vitro propagation of Dendrobium fimbriatum and their genetic stability assessment using molecular markers.

DNA barcoding and genetic fidelity assessment of micropropagated Aenhenrya rotundifolia (Blatt.) C.S. Kumar and F.N. Rasm.: a critically endangered jewel orchid

Aenhenrya rotundifolia is a critically endangered terrestrial jewel orchid. It is monotypic and endemic to evergreen forests of southern western ghats of India. In the present study, identification of this plant species is validated with DNA barcoding using matK and rbcL chloroplast markers. Further, germ-free juvenile axillary bud explants were cultured on Mitra medium supplemented with different kinds of cytokinins like 6-benzyladenine, 6-furfurylaminopurine, N⁶-(Δ²-isopentyl) adenine, thidiazuron, zeatin and meta-topolin as well as auxins such as α-naphthaleneacetic acid, indole-3-acetic acid and indole-3-butyric acid at different concentrations and combinations for successful proliferation and establishment in vitro. After 12 weeks of culture, axillary bud explants produced an average of 30.12 ± 0.71 shoots per explant, 3.87 ± 0.06 cm shoot length, 1671 ± 2.82 mg fresh mass of proliferated shoots with a proliferation frequency of 100% on Mitra medium supplemented with 6.20 µM meta-topolin and 2.25 µM thidiazuron. No root formation was observed in in vitro proliferated microshoots. However, tiny hair like projections were observed in some elongated shoots on Mitra medium pertaining to 5.37 µM NAA. The tiny hair like structure bearing plantlets were hardened and acclimatized with 100% survival rate in the polytunnel chamber. After 8-10 months of establishment ex vitro, flowering was observed. Additionally, the genetic fidelity of in vitro derived plants was tested with ISSR and SCoT marker profiling. The test results revealed that the plants derived from the protocol has 99% genetic similarity to that of the donor mother plant. This study can be applied in forensic interventions of this species, describes the maintenance of germplasm in vitro and establishment of new viable population in its original habitats by restoring existing sites of this critically endangered jewel orchid.

Micropropagation of Alocasia longiloba Miq and Comparative Antioxidant Properties of Ethanolic Extracts of the Field-Grown Plant, In Vitro Propagated and In Vitro-Derived Callus

In this study, an efficient micropropagation protocol was developed for A. longiloba and the antioxidant properties of field-grown plant, in vitro-derived greenhouse-grown plant and in vitro-derived callus extracts were compared. The A. longiloba seeds tested using tetrazolium chloride salt exhibited 89% viability. Due to poor germination capacity of A. longiloba seeds, the seeds were treated with gibberellic acid (GA₃) or sulfuric acid (H₂SO₄). The maximum seed germination of 87% was observed at 30% H₂SO₄ treatment after 19.00 d, whereas GA₃ treatment showed maximum germination of 53% after 22 d. In vitro shoot multiplication was carried out using various types of cytokinins alone or in combination with auxin. Among them, 6-benzyl amino purine (BAP) single treatment was found to be the best hormone. The highest shoot-length (7.26 cm) and maximum number of shoots per explant (18) were recorded at 3-mg L⁻¹ BAP. For in vitro rooting, indole-3-acetic acid at 0.5-mg L⁻¹ was found to be the optimum concentration. Callus was induced using various types of auxins alone or in combinations with cytokinins. The highest percentage of callus of 91 and fresh weight of 6 g was obtained with 3-mg L⁻¹ IAA. The plantlets produced in the current study were subjected to acclimatization. The combination of topsoil and peat moss at 1:2 ratio was found to be the best soil media. In this study, in vitro-derived callus extract showed the highest phenolic content (538 mg GAE), followed by extracts of field-grown plant parts, i.e., fruit and petiole (504 and 300 mg GAE) while in vitro plant extract showed the lowest (98 mg GAE). Meanwhile, the highest flavonoids was recorded in petiole extract. Comparative antioxidant activity study shows, in vitro-derived callus exhibited better DPPH-radical-scavenging activity (IC₅₀: 0.113-mg mL⁻¹) whereas the extracts of petiole, fruit and in vitro plant showed 0.126-, 0.137- and 0.173-mg mL⁻¹, respectively. At the same time, the fruit extract showed better (IC₅₀: 0.088-mg mL⁻¹) ABTS radical scavenging activity than all extracts tested. In conclusion, the in vitro-derived callus extract could be favored for high TPC and better DPPH scavenging activity. Hence, the present study was conducted to establish an efficient micropropagation protocol and to compare the antioxidant activity of the field-grown plant, in vitro plant and in vitro derived callus extracts of A. longiloba.

Droplet-vitrification of Aranda Broga Blue orchid: Role of ascorbic acid on the antioxidant system and genetic fidelity assessments via RAPD and SCoT markers

A droplet-vitrification cryopreservation protocol has been successfully developed for Aranda Broga Blue orchid hybrid using protocorm-like bodies (PLBs). However, maximum growth regeneration percentage was recorded at 5% only based on previous report. Thus, to improve growth recovery of cryopreserved PLBs, cryopreservation stages were supplemented with ascorbic acid, tested at 50, 100 and 150 mg/L. However, results demonstrated that exogenous ascorbic acid was not favorable in regeneration of cryopreserved explants (maximum value of 1.67 % with 50 mg/L ascorbic acid supplementation). Total soluble protein and various antioxidant enzyme activities such as catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX) were evaluated after each cryopreservation stages in conjunction with the application of exogenous ascorbic acid. Addition of antioxidant must be carefully evaluated and its application may not guarantee successful growth recovery. RAPD and SCoT molecular analysis confirmed the genetic stability of regenerated cryopreserved PLBs as no polymorphism was detected compared to control PLBs culture.

Mining of miRNAs from EST data in Dendrobium nobile

Dendrobium nobile is an orchid species highly popular for its therapeutic properties and is often used as a medicinal herb. Documenting miRNA-target associations in D. nobile is an important step to facilitate functional genomics studies in this species. Therefore, it is of interest to identify miRNA sequences from EST data available in public databases using known techniques and tools. We report 14 potential miRNAs from three ESTs of D. nobile. They belong to 3 miRNA families (miR390, miR528 and miR414) linking to transcription factor regulation, signal transduction, DNA and protein binding, and various cellular processes covering 34 different metabolic networks in KEGG. These results help in the understanding of miRNA-mRNAs functional networks in Dendrobium nobile.

Phenolic compounds, antioxidant capacity and antimutagenic activity in different growth stages of in vitro raised plants of Origanum vulgare L

Efficient micropropagation procedure was developed for Origanum vulgare, a high-value culinary herb, and the phytochemicals, phenolic content, antioxidant and antimutagenic activity of leaf and stem, derived from different growing stages were analyzed. The agar solidified Murashige and Skoog (MS) medium supplemented with a combination of 6-benzylaminopurine and α-naphthaleneacetic acid was optimized as best shoot-multiplication-medium. Shoots were rooted best on 1/2 strength MS medium supplemented with 50 µM indole-3-butyric acid (IBA). The plantlets were successfully acclimatized ex vitro in a soil, sand and farmyard manure mixture (2:1:1 v/v/v) with 100% survival rate in greenhouse. The total anthocyanin and total phenolic content were observed significantly higher in leaves of in vitro-raised plants. However, total tannin, flavonoid and antioxidant activity remained higher in leaves of mother plant maintained under ployhouse condition. All the plant extracts have shown significant antimutagenic activity except in vitro-growing plants. A total of 13 polyphenolic compounds were detected in different extracts using high performance liquid chromatography. Among these, catechin was detected maximum in in vitro-growing cultures and chlorogenic acid in leaves of mother plant. These findings will help the farmers, medicinal plant growers, and industries for mass multiplication and effective extraction of phytochemicals from O. vulgare.

Thidiazuron-induced abnormalities in plant tissue cultures

Thidiazuron (TDZ) is a proven effective and potent synthetic plant growth regulator for organogenic, regeneration, and developmental pathways, including axillary and adventitious shoot proliferation, somatic embryogenesis, and in vitro flowering. TDZ has facilitated the establishment of in vitro cultures for several plant species, especially woody and recalcitrant plants, which has enabled their genetic transformation and improvement. Despite the effectiveness and advantages of using TDZ, several drawbacks are associated with its application in plant tissue culture. This review addresses the morphological, physiological, and cytogenetic abnormalities associated with the use of TDZ in vitro, and provides a summary of these abnormalities in several plant species.

In vitro plant tissue culture: means for production of biological active compounds

MAIN CONCLUSION

Plant tissue culture as an important tool for the continuous production of active compounds including secondary metabolites and engineered molecules. Novel methods (gene editing, abiotic stress) can improve the technique. Humans have a long history of reliance on plants for a supply of food, shelter and, most importantly, medicine. Current-day pharmaceuticals are typically based on plant-derived metabolites, with new products being discovered constantly. Nevertheless, the consistent and uniform supply of plant pharmaceuticals has often been compromised. One alternative for the production of important plant active compounds is in vitro plant tissue culture, as it assures independence from geographical conditions by eliminating the need to rely on wild plants. Plant transformation also allows the further use of plants for the production of engineered compounds, such as vaccines and multiple pharmaceuticals. This review summarizes the important bioactive compounds currently produced by plant tissue culture and the fundamental methods and plants employed for their production.

Insights into nuclear DNA content, hydrogen peroxide and antioxidative enzyme activities during transverse thin cell layer organogenesis and ex vitro acclimatization of Malaxis wallichii, a threatened medicinal orchid

Malaxis wallichii (Lindl.) Deb, a small, perennial, monopodial, terrestrial orchid, is endemic to tropical Himalayas at an altitude of 1200-2000 m asl. The pseudobulbs are important ingredients of century old drug 'Ashtavarga' and a polyherbal energetic tonic 'Chyavanprash'. An efficient genetically stable in vitro propagation protocol using transverse thin cell layer culture system was established for M. wallichii. In the present report, meta-topolin alone proved to be three times more beneficial compared to other routinely used cytokinins in inducing highest number of shoot buds, plant height and growth of regenerated shoots. The highest regeneration frequency (89%) along with maximum number of adventitious shoots per explant (22.5 ± 0.6) was observed in MS medium supplemented with 1.0 mg/l meta-topolin and 0.5 mg/l α-naphthalene acetic acid. Highest rooting frequency with highest number of roots (8.66 ± 0.3) was achieved in half-strength MS medium fortified with 1.0 mg/l indole acetic acid. Clonal stability of in vitro-derived plantlets was evaluated and compared to donor plant using intron splice junction (ISJ) markers and flow cytometry. ISJ markers revealed 4.76% clonal variability indicating high degree of genetic stability amongst the in vitro-derived regenerants. The nuclear DNA content of M. wallichii (2n) was found to be 2C = 2.760 ± 0.02 pg and therefore, 1349.64 Mbp (1C). Flow cytometry analysis of actively growing young and mature leaves from donor as well as in vitro-derived plantlets revealed presence of three peaks corresponding to 2C, 4C and 8C, while 2C was the most abundant. In the present investigation, there was no significant difference in the 2C DNA content between the mother and in vitro-derived plants; however, the frequency of endopolyploid cells varied in young and adult plants. An increased H2O2 content as well as lipid peroxidation activities were observed during early stages of acclimatization which declined afterwards. The enhanced activities of antioxidant enzymes like superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase in acclimatized plantlets as compared to in vitro-grown ones revealed their active involvement in growth and development against oxidative stress under external adverse environment.

Studies on secondary metabolite profiling, anti-inflammatory potential, in vitro photoprotective and skin-aging related enzyme inhibitory activities of Malaxis acuminata, a threatened orchid of nutraceutical importance

Malaxis acuminata D. Don., a small, terrestrial orchid, is endemic to tropical Himalayas at an altitude of 1200-2000m asl. The dried pseudobulbs are important ingredients of century old ayurvedic drug 'Ashtavarga' and a polyherbal immune-booster nutraceutical 'Chyavanprash', known to restore vigour, vitality and youthfulness. Considering tremendous medicinal importance of this threatened orchid species, a detailed study was undertaken for the first time to address its antioxidant potential, secondary metabolite contents and biological activities against skin-aging related enzymes (anti-collagenase, anti-elastase, anti-tyrosinase and xanthine oxidase) and anti-inflammatory activity (5-lipoxygenase and hyaluronidase) in different plant parts of wild and in vitro-derived plants of M. acuminata. Methanolic leaf and stem extracts were further evaluated for in vitro photoprotective activity against UV-B and UV-A radiations. Furthermore, secondary metabolite profiling of various plant parts was carried out by Gas Chromatography Mass Spectrometry (GC-MS). A significantly higher antioxidant potential (DPPH, metal chelating and ABTS^•+) with a comparative higher yield of secondary metabolites was observed in in vitro-derived plantlets as compared to the wild plants. Among various solvent systems used, methanolic leaf and stem extracts showed promising inhibitory activity against major skin aging-related enzymes and anti-inflammatory potential. Methanolic leaf and stem extracts of both wild and in vitro-derived plants showed promising photoprotective activity against UV-B and UV-A radiations in vitro with comparatively higher sun protection factor (SPF). Furthermore, GC-MS analysis of methanolic extracts of leaves and stems of wild as well as in vitro-derived plantlets revealed presence of many bioactive metabolites such as, dietary fatty acids, α-hydroxy acids, phenolic acids, sterols, amino acids, sugars and glycosides which substantially explain the use of M. acuminata as one of the potential rejuvenator and anti-aging ingredient in many Ayurvedic formulations.

Structural Analysis and Immuno-Stimulating Activity of an Acidic Polysaccharide from the Stems of Dendrobium nobile Lindl

Dendrobium nobile Lindl., an epiphytic herb distributed in the Southeast Asia, is used as a tonic and antipyretic herbal medicine in China. In this study, a water-soluble acidic heteropolysaccharide, DNP-W4, containing mannose, glucose, galactose, xylose, rhamnose, and galacturonic acid, in the molar ratios of 1.0:4.9:2.5:0.5:1.0:0.9, was obtained from the stems of Dendrobium nobile Lindl. Using methylation analysis, partial acid hydrolysis, pectolyase treatment, NMR, and ESI-MS, the structure of DNP-W4 was elucidated. The obtained data indicated that DNP-W4 was a complex heteropolysaccharide and possessed a backbone composed of (1→4)-linked β-d-Glcp, (1→6)-linked β-d-Glcp, and (1→6)-linked β-d-Galp, with substitutes at O-4/6 of Glcp residues and O-3 of Galp. The branches of DNP-W4 were composed of terminal Manp, (1→6)-linked β-d-Manp, (1→3)-linked β-d-Glcp, β-d-Glcp, β-d-Galp, (1→4)-linked α-d-GalAp, (1→2)-linked α-L-Rhap, and Xylp. DNP-W4 had little immunological activities, but its derivatives had immuno-stimulating activities to some extent.

Phenolic Compounds and Antioxidant Activity of Phalaenopsis Orchid Hybrids

Phalaenopsis spp. is the most commercially and economically important orchid, but their plant parts are often left unused, which has caused environmental problems. To date, reports on phytochemical analyses were most available on endangered and medicinal orchids. The present study was conducted to determine the total phenolics, total flavonoids, and antioxidant activity of ethanol extracts prepared from leaves and roots of six commercial hybrid Phalaenopsis spp. Leaf extracts of "Chian Xen Queen" contained the highest total phenolics with a value of 11.52 ± 0.43 mg gallic acid equivalent per g dry weight and the highest total flavonoids (4.98 ± 0.27 mg rutin equivalent per g dry weight). The antioxidant activity of root extracts evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging assay and β-carotene bleaching method was higher than those of the leaf extracts. Eleven phenolic compounds were identified, namely, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, vanillin, ferulic acid, sinapic acid, p-coumaric acid, benzoic acid, and ellagic acid. Ferulic, p-coumaric and sinapic acids were concentrated largely in the roots. The results suggested that the root extracts from hybrid Phalaenopsis spp. could be a potential source of natural antioxidants. This study also helps to reduce the amount of this orchid waste in industrial production, as its roots can be exploited for pharmaceutical purposes.

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.