Biotechnological production of centellosides in cell cultures ofCentella asiatica(L) Urban

An update on biotechnological intervention mediated by plant tissue culture to boost secondary metabolite production in medicinal and aromatic plants

Since prehistoric times, medicinal and aromatic plants (MAPs) have been employed for various therapeutic purposes due to their varied array of pharmaceutically relevant bioactive compounds, i.e. secondary metabolites. However, when secondary metabolites are isolated directly from MAPs, there is occasionally very poor yield and limited synthesis of secondary metabolites from particular tissues and certain developmental stages. Moreover, many MAPs species are in danger of extinction, especially those used in pharmaceuticals, as their natural populations are under pressure from overharvesting due to the excess demand for plant-based herbal remedies. The extensive use of these metabolites in a number of industrial and pharmaceutical industries has prompted a call for more research into increasing the output via optimization of large-scale production using plant tissue culture techniques. The potential of plant cells as sources of secondary metabolites can be exploited through a combination of product recovery technology research, targeted metabolite production, and in vitro culture establishment. The plant tissue culture approach provides low-cost, sustainable, continuous, and viable secondary metabolite production that is not affected by geographic or climatic factors. This study covers recent advancements in the induction of medicinally relevant metabolites, as well as the conservation and propagation of plants by advanced tissue culture technologies.

Insights into enhancing Centella asiatica organ cell biofactories via hairy root protein profiling

Recent advancements in plant biotechnology have highlighted the potential of hairy roots as a biotechnological platform, primarily due to their rapid growth and ability to produce specialized metabolites. This study aimed to delve deeper into hairy root development in C. asiatica and explore the optimization of genetic transformation for enhanced bioactive compound production. Previously established hairy root lines of C. asiatica were categorized based on their centelloside production capacity into HIGH, MID, or LOW groups. These lines were then subjected to a meticulous label-free proteomic analysis to identify and quantify proteins. Subsequent multivariate and protein network analyses were conducted to discern proteome differences and commonalities. Additionally, the quantification of rol gene copy numbers was undertaken using qPCR, followed by gene expression measurements. From the proteomic analysis, 213 proteins were identified. Distinct proteome differences, especially between the LOW line and other lines, were observed. Key proteins related to essential processes like photosynthesis and specialized metabolism were identified. Notably, potential biomarkers, such as the Tr-type G domain-containing protein and alcohol dehydrogenase, were found in the HIGH group. The presence of ornithine cyclodeaminase in the hairy roots emerged as a significant biomarker linked with centelloside production capacity lines, indicating successful Rhizobium-mediated genetic transformation. However, qPCR results showed an inconsistency with rol gene expression levels, with the HIGH line displaying notably higher expression, particularly of the rolD gene. The study unveiled the importance of ornithine cyclodeaminase as a traceable biomarker for centelloside production capacity. The strong correlation between this biomarker and the rolD gene emphasizes its potential role in optimizing genetic transformation processes in C. asiatica.

Safety Assessment of Centella asiatica-Derived Ingredients as Used in Cosmetics

The Expert Panel for Cosmetic Ingredient Safety (Panel) assessed the safety of 9 Centella asiatica-derived ingredients, which reportedly function primarily as skin conditioning agents in cosmetic products. The Panel reviewed relevant data relating to the safety of these ingredients. The Panel concluded that Centella Asiatica Extract, Centella Asiatica Callus Culture, Centella Asiatica Flower/Leaf/Stem Extract, Centella Asiatica Leaf Cell Culture Extract, Centella Asiatica Leaf Extract, Centella Asiatica Leaf Water, Centella Asiatica Meristem Cell Culture, Centella Asiatica Meristem Cell Culture Extract, and Centella Asiatica Root Extract are safe in the present practices of use and concentration in cosmetics, as described in this safety assessment, when formulated to be non-sensitizing.

Biotechnological and endophytic-mediated production of centellosides in Centella asiatica

In vitro culture of a plant cell, tissue and organ is a marvellous, eco-friendly biotechnological strategy for the production of phytochemicals. With the emergence of recent biotechnological tools, genetic engineering is now widely practiced enhancing the quality and quantity of plant metabolites. Triterpenoid saponins especially asiaticoside and madecassoside of Centella asiatica (L.) Urb. are popularly known for their neuroprotective activity. It has become necessary to increase the production of asiaticoside and madecassoside because of their high pharmaceutical and industrial demand. Thus, the review aims to provide efficient biotechnological tools along with proper strategies. This review also included a comparative analysis of various carbon sources and biotic and abiotic elicitors. The vital roles of a variety of plant growth regulators and their combinations have also been evaluated at different in vitro growth stages of Centella asiatica. Selection of explants, direct and callus-mediated organogenesis, root organogenesis, somatic embryogenesis, synthetic seed production etc. are also highlighted in this study. In a nutshell, this review will present the research outcomes of different biotechnological interventions used to increase the yield of triterpenoid saponins in C. asiatica. KEY POINTS: • Critical and updated assessment on in vitro biotechnology in C. asiatica. • In vitro propagation of C. asiatica and elicitation of triterpenoid saponins production. • Methods for mass producing C. asiatica.

Biotechnological Intervention and Secondary Metabolite Production in Centella asiatica L

Centella asiatica L., commonly known as Gotu kola, Indian pennywort, and Asiatic pennyworts, is an herbaceous perennial plant that belongs to the family Apiaceae and has long been used in the traditional medicine system. The plant is known to produce a wide range of active metabolites such as triterpenoids including asiatic acid, asiaticoside, brahmoside, and madecassic acid along with other constituents including centellose, centelloside, and madecassoside, etc., which show immense pharmacological activity. Due to its beneficial role in neuroprotection activity, the plant has been considered as a brain tonic. However, limited cultivation, poor seed viability with low germination rate, and overexploitation for decades have led to severe depletion and threatened its wild stocks. The present review aimed to provide up-to-date information on biotechnological tools applied to this endangered medicinal plant for its in vitro propagation, direct or indirect regeneration, synthetic seed production, strategies for secondary metabolite productions including different elicitors. In addition, a proposed mechanism for the biosynthesis of triterpenoids is also discussed.

Using machine learning to link the influence of transferred Agrobacterium rhizogenes genes to the hormone profile and morphological traits in Centella asiatica hairy roots

Hairy roots are made after the integration of a small set of genes from Agrobacterium rhizogenes in the plant genome. Little is known about how this small set is linked to their hormone profile, which determines development, morphology, and levels of secondary metabolite production. We used C. asiatica hairy root line cultures to determine the putative links between the rol and aux gene expressions with morphological traits, a hormone profile, and centelloside production. The results obtained after 14 and 28 days of culture were processed via multivariate analysis and machine-learning processes such as random forest, supported vector machines, linear discriminant analysis, and neural networks. This allowed us to obtain models capable of discriminating highly productive root lines from their levels of genetic expression (rol and aux genes) or from their hormone profile. In total, 12 hormones were evaluated, resulting in 10 being satisfactorily detected. Within this set of hormones, abscisic acid (ABA) and cytokinin isopentenyl adenosine (IPA) were found to be critical in defining the morphological traits and centelloside content. The results showed that IPA brings more benefits to the biotechnological platform. Additionally, we determined the degree of influence of each of the evaluated genes on the individual hormone profile, finding that aux1 has a significant influence on the IPA profile, while the rol genes are closely linked to the ABA profile. Finally, we effectively verified the gene influence on these two specific hormones through feeding experiments that aimed to reverse the effect on root morphology and centelloside content.

Assessment of major centelloside ratios in Centella asiatica accessions grown under identical ecological conditions, bioconversion clues and identification of elite lines

Centellosides viz., asiatic acid, madecassic acid, asiaticoside, madecassoside, are the major bioactive molecules in Centella asiatica. In this study madecassic acid:asiatic acid, madecassoside:asiaticoside (C6-hydroxylation versus non-hydroxylation) and asiaticoside:asiatic acid, madecassoside:madecassic acid (C28-glycoside versus aglycone) ratios in 50 C. asiatica accessions originally collected from their natural habitats in south India and grown under identical ecological conditions for six generations were determined using validated HPTLC-densitometry protocols. Asiatic acid, madecassic acid, asiaticoside and madecassoside contents ranged from 0.00-0.29% (average 0.03 ± 0.06%; 28 accessions recorded asiatic acid content as zero), 0.02-0.72% (0.12 ± 0.13%), 0.04-2.41% (0.44 ± 0.52%) and 0.15-5.27% (1.59 ± 1.26%), respectively. Distinctly, C6-hydroxylated (madecassic acid:asiatic acid 4.00, madecassoside:asiaticoside 3.61) and C28-glycosylated (asiaticoside:asiatic acid 14.67, madecassoside: madecassic acid 13.25) centellosides dominated over the respective non-derivatized entities. Our results infer that both C6-hydroxylation by CYP450-dependent monooxygenases and C28-glycosylation by UDP-Glc glucosyltransferases are dominant bioconversion steps in C. asiatica. Besides, this study discovered six elite lines of C. asiatica, with their (asiaticoside + madecassoside) contents above the industrial benchmark (≥ 4%) from south India. Two elite clones with asiaticoside contents ≥ 2% were also identified. Standardization of the agrotechniques of these elite lines could lead to their industrial applications. Further, this study emphasizes the need for standardizing all four centellosides as biomarkers in C. asiatica raw drugs, pharmaceutical and cosmetic products.

Impact of potential stimulants on asiaticoside and madecassoside levels and expression of triterpenoid-related genes in axenic shoot cultures of Centella asiatica (L.) Urb

The triterpenoid saponins, asiaticoside and madecassoside from Centella asiatica (L.) Urb. are known to have a wide range of applications in pharmaceutical and cosmetic industries. The effect of addition of Potential Metabolite Stimulants (PMSs) - casein acid hydrolysate, meat peptone, salicylic acid, copper sulphate, and silver nitrate, on the concentrations of these saponins and transcript levels of associated genes encoding important biosynthetic enzymes, was assessed in axenic shoot cultures of C. asiatica. Among the stimulants, silver nitrate induced asiaticoside content approximately 6-fold increase in madecassoside levels, after three weeks post-treatment with a decrease in biomass compared to its control. Gene expression analysis of essential genes involved in triterpenoid synthesis such as β-amyrin synthase showed an upregulation of approximately 50-fold at the third week of silver nitrate treatment compared to control. These findings suggest that silver nitrate can act as a metabolite stimulant, to enhance the formation of triterpenoids in axenic shoot culture of C. asiatica, which could be utilized in studying the regulation of terpenoid biosynthesis and biotechnological application for the increased production of these bioactive molecules.

Powerful Plant Antioxidants: A New Biosustainable Approach to the Production of Rosmarinic Acid

Modern lifestyle factors, such as physical inactivity, obesity, smoking, and exposure to environmental pollution, induce excessive generation of free radicals and reactive oxygen species (ROS) in the body. These by-products of oxygen metabolism play a key role in the development of various human diseases such as cancer, diabetes, heart failure, brain damage, muscle problems, premature aging, eye injuries, and a weakened immune system. Synthetic and natural antioxidants, which act as free radical scavengers, are widely used in the food and beverage industries. The toxicity and carcinogenic effects of some synthetic antioxidants have generated interest in natural alternatives, especially plant-derived polyphenols (e.g., phenolic acids, flavonoids, stilbenes, tannins, coumarins, lignins, lignans, quinines, curcuminoids, chalcones, and essential oil terpenoids). This review focuses on the well-known phenolic antioxidant rosmarinic acid (RA), an ester of caffeic acid and (R)-(+)-3-(3,4-dihydroxyphenyl) lactic acid, describing its wide distribution in thirty-nine plant families and the potential productivity of plant sources. A botanical and phytochemical description is provided of a new rich source of RA, Satureja khuzistanica Jamzad (Lamiaceae). Recently reported approaches to the biotechnological production of RA are summarized, highlighting the establishment of cell suspension cultures of S. khuzistanica as an RA chemical biofactory.

Plant triterpenoid saponins: biosynthesis, in vitro production, and pharmacological relevance

The saponins are a diverse class of natural products, with a broad scale distribution across different plant species. Chemically characterized as triterpenoid glycosides, they posses a 30C oxidosqualene precursor-based aglycone moiety (sapogenin), to which glycosyl residues are subsequently attached to yield the corresponding saponin. Based on the chemically distinct aglycone moieties, broadly, they are divided into triterpenoid saponins (dammaranes, ursanes, oleananes, lupanes, hopanes, etc.) and the sterol glycosides. This review aims to present in detail the biosynthesis patterns of the different aglycones from a common precursor and their glycosylation patterns to yield the functionally active glycoside. The review also presents recent advances in the pharmacological activities of these saponins, particularly as potent anti-neoplastic pharmacophores, antioxidants, or anti-viral/antibacterial agents. Since alternate production pedestals for these pharmacologically important triterpenes via cell and tissue cultures are an attractive option for their sustainable production, recent trends in the variety and scale of in vitro production of plant triterpenoids have also been discussed.

Elicitation with methyl jasmonate combined with cultivation in the Plantform™ temporary immersion bioreactor highly increases the accumulation of selected centellosides and phenolics in Centella asiatica (L.) Urban shoot culture

Centella asiatica (L.) Urban is an important pharmacopoeial plant used not only in medicine but also in cosmetology. C. asiatica agitated shoot cultures were established to study the influence of ethephon, methyl jasmonate, l-phenylalanine (Eth 50 µM, MeJa 50 µM, L-Phe 2.4 g/L of medium, respectively; seven variants of the supplementation) on the accumulation of secondary metabolites: the main centellosides (asiaticoside and madecassoside) and selected phenolic acids, and flavonoids in the biomass. Microshoots were harvested two and six days after the supplementation. Secondary metabolites were analyzed in methanolic extracts by UPLC-MS/MS (centellosides) and by HPLC-DAD (phenolics). In comparison with the reference cultures, the concentrations of individual secondary metabolites increased as follows: centellosides up to 5.6-fold (asiaticoside), phenolic acids up to 122-fold (p-coumaric acid) and flavonoids up to 22.4-fold (kaempherol). The highest production increase of individual compounds was observed for different variants of supplementation. Variant C (50 µM MeJa), the most optimal for centellosides and flavonoid accumulation, was selected for the experiment with bioreactors. Bioreactor Plantform™, compared to RITA^® system and agitated cultures, appeared to be the most advantageous for secondary metabolites production in C. asiatica shoot cultures. The phenolic acid, flavonoid, centelloside, and total secondary metabolite productivity in Plantform™ system is 1.8-fold, 1.7-fold, 2.8-fold, 2.1-fold, respectively, higher than in MeJa elicitated agitated cultures, and 4.3-fold, 7.3-fold, 12.2-fold, 7.2-fold, respectively, higher than in control agitated cultures.

Protection of mouse brain from paracetamol-induced stress by Centella asiatica methanol extract

ETHNOPHARMACOLOGICAL RELEVANCE

Centella asiatica (CA) is a medicinal herb traditionally used as a brain tonic in Ayurvedic medicine. Various ethnomedical leads revealed the effective use of CA in the treatment of symptoms associated to oxidative stress and inflammation.

AIM OF THE STUDY

The aim of this study was to evaluate the therapeutic ability of CA methanol extract (CAM) in protecting mouse brain and astrocytes from oxidative stress and inflammation induced by Paracetamol, and thus to substantiate the allied traditional/ethnomedical claims of CA.

MATERIALS AND METHODS

Chemical profiling of CAM and quantification of its major constituents were carried out by HPTLC-densitometry. Mice were administered with CAM and Paracetamol in various combinations, and oxidative stress parameters (lipid peroxidation, radical scavenging) as well as nitric oxide stress were estimated from isolated mouse brain. Cellular toxicity was investigated by apoptosis/necrosis in primary astrocytes isolated from brain tissues of mouse (which was challenged by CAM/Paracetamol) by flow cytometry and fluorescent microscopy. Expression of inflammatory cytokine mediators (monocyte chemo attractant protein 1, interleukin 1, interferon γ, tumor necrosis factor β, interleukin 10 and mitogen activated protein kinase 14 gene) in CAM/Paracetamol administered mouse brain tissues was analyzed by real time PCR. Mouse brain tissues challenged by CAM/Paracetamol were also assessed for gross and histopathology. In addition, staining with acridine orange was carried out in C6 cell lines treated with CAM, and viewed under fluorescent microscopy.

RESULTS

Paracetamol elicited reactive oxygen species generation was revealed through Ferric Reducing Antioxidant Power (FRAP) activity. CAM reversed the Paracetamol induced free radical and reactive nitrogen species production and increased the scavenging activity which was more pronounced at the higher dose (80 mg/kg b.wt). CAM negated the Paracetamol-induced damage by inhibiting expression of pro-inflammatory cytokines (MCP 1, IL 1, TNF β), and increasing the expression of the anti-inflammatory cytokine (IL 10) profoundly. Interestingly, MAPK 14 gene expression was decreased gradually and became same as normal control with increase in the dose of CAM. Also, it was evident that CAM protected mouse primary astrocytes from Paracetamol by maintaining a normal morphology. Similarly, apoptosis of primary astrocytes (treated with Paracetamol/CAM) decreased with the increase in CAM dose (80 mg/kg b.wt.) which was evident from flow cytometric data. Severe brain damage in the form of lesions was apparent from the histology of Paracetamol alone treated mouse brain. Whereas, CAM treated together with Paracetamol upturned these lesions. Surprisingly, CAM alone proved to be cytotoxic to C6 Glioma cells.

CONCLUSIONS

CAM showed antioxidant and anti-inflammatory effects (which were pronounced at higher doses) against Paracetamol-induced oxidative stress and associated inflammation in mouse brain. The underlying mechanisms may be mediated by inhibiting the pro-inflammatory cytokines TNF β, IL 1 and MCP 1 via regulation of the antioxidant mediated INF γ and MAPK 14 gene signalling pathways. The major bioactive constituents in CAM are the triterpenoid saponins, asiaticoside and madecassoside. The present results provide pharmacological evidence that CAM acts as an antioxidant and anti-inflammatory agent. Furthermore, this study validates the use of CA as an antioxidant and anti-inflammatory agent in ethnomedicine.

Centella asiatica - Phytochemistry and mechanisms of neuroprotection and cognitive enhancement

This review describes in detail the phytochemistry and neurological effects of the medicinal herb Centella asiatica (L.) Urban. C. asiatica is a small perennial plant that grows in moist, tropical and sub-tropical regions throughout the world. Phytochemicals identified from C. asiatica to date include isoprenoids (sesquiterpenes, plant sterols, pentacyclic triterpenoids and saponins) and phenylpropanoid derivatives (eugenol derivatives, caffeoylquinic acids, and flavonoids). Contemporary methods for fingerprinting and characterization of compounds in C. asiatica extracts include liquid chromatography and/or ion mobility spectrometry in conjunction with high-resolution mass spectrometry. Multiple studies in rodent models, and a limited number of human studies support C. asiatica's traditional reputation as a cognitive enhancer, as well as its anxiolytic and anticonvulsant effects. Neuroprotective effects of C.asiatica are seen in several in vitro models, for example against beta amyloid toxicity, and appear to be associated with increased mitochondrial activity, improved antioxidant status, and/or inhibition of the pro-inflammatory enzyme, phospholipase A2. Neurotropic effects of C. asiatica include increased dendritic arborization and synaptogenesis, and may be due to modulations of signal transduction pathways such as ERK1/2 and Akt. Many of these neurotropic and neuroprotective properties of C.asiatica have been associated with the triterpene compounds asiatic acid, asiaticoside and madecassoside. More recently, caffeoylquinic acids are emerging as a second important group of active compounds in C. asiatica, with the potential of enhancing the Nrf2-antioxidant response pathway. The absorption, distribution, metabolism and excretion of the triterpenes, caffeoylquinic acids and flavonoids found in C. asiatica have been studied in humans and animal models, and the compounds or their metabolites found in the brain. This review highlights the remarkable potential for C. asiatica extracts and derivatives to be used in the treatment of neurological conditions, and considers the further research needed to actualize this possibility.

An optimized biotechnological system for the production of centellosides based on elicitation and bioconversion of Centella asiatica cell cultures

Centella asiatica is a herbaceous plant of Asian traditional medicine. Besides wound healing, this plant is recommended for the treatment or care of various skin conditions such as dry skin, leprosy, varicose ulcers, eczema, and/or psoriasis. Triterpene saponins, known as centellosides, are the main metabolites associated with these beneficial effects. Considering the interest in these high value active compounds, there is a need to develop biosustainable and economically viable processes to produce them. Previous work using C. asiatica plant cell culture technology demonstrated the efficient conversion of amyrin derivatives into centellosides, opening a new way to access these biomolecules. The current study was aimed at increasing the production of centellosides in C. asiatica plant cell cultures. Herein, we report the application of a new elicitor, coronatine, combined with the addition of amyrin-enriched resins as potential sustainable precursors in the centelloside pathway, for a positive synergistic effect on centelloside production. Our results show that coronatine is a powerful elicitor for increasing centelloside production and that treatments with sustainable natural sources of amyrins enhance centelloside yields. This process can be scaled up to an orbitally shaken CellBag, thereby increasing the capacity of the system for producing biomass and centellosides.

Stimulatory Effects of Acibenzolar-S-Methyl on Chlorogenic Acids Biosynthesis in Centella asiatica Cells

Centella asiatica is a perrenial herb that grows in tropical regions with numerous medicinal properties mostly attributed to the presence of pentacyclic triterpenoids. Interestingly, this plant also possess a significant amount of phenylpropanoid-derived chlorogenic acids (CGAs) that have recently been reported to confer neuroprotective properties. In a biotechnological attempt to increase the biosynthesis of CGA-derivatives in cultured Centella cells, acibenzolar-S-methyl was applied as a xenobiotic inducer in combination with quinic acid and shikimic acid as precursor molecules. Applying a semi-targeted metabolomics-based approach, time and concentration studies were undertaken to evaluate the effect of the manipulation on cellular metabolism leading to CGA production. Phytochemical extracts were prepared using methanol and analyzed using a UHPLC-qTOF-MS platform. Data was processed and analyzed using multivariate data models. A total of four CGA-derivatives, annotated as trans-5-feruloylquinic acid, 3,5 di-caffeoylquinic acid, 3,5-O-dicaffeoyl-4-O-malonylquinic acid (irbic acid) and 3-caffeoyl, 5-feruloylquinic acid, were found to be upregulated by the acibenzolar-S-methyl treatment. To the best of our knowledge, this is the first report on the induction of CGA derivatives in this species. Contrary to expectations, the effects of precursor molecules on the levels of the CGAs were insignificant. However, a total of 16 metabolites, including CGA derivatives, were up-regulated by precursor treatment. Therefore, this study shows potential to biotechnologically manipulate C. asiatica cells to increase the production of these health beneficial CGAs.

Chlorogenic Acids Biosynthesis in Centella asiatica Cells Is not Stimulated by Salicylic Acid Manipulation

Exogenous application of synthetic and natural elicitors of plant defence has been shown to result in mass production of secondary metabolites with nutraceuticals properties in cultured cells. In particular, salicylic acid (SA) treatment has been reported to induce the production of phenylpropanoids, including cinnamic acid derivatives bound to quinic acid (chlorogenic acids). Centella asiatica is an important medicinal plant with several therapeutic properties owing to its wide spectrum of secondary metabolites. We investigated the effect of SA on C. asiatica cells by monitoring perturbation of chlorogenic acids in particular. Different concentrations of SA were used to treat C. asiatica cells, and extracts from both treated and untreated cells were analysed using an optimised UHPLC-QTOF-MS/MS method. Semi-targeted multivariate data analyses with the aid of principal component analysis (PCA) and orthogonal projection to latent structures-discriminant analysis (OPLS-DA) revealed a concentration-dependent metabolic response. Surprisingly, a range of chlorogenic acid derivatives were found to be downregulated as a consequence of SA treatment. Moreover, irbic acid (3,5-O-dicaffeoyl-4-O-malonilquinic acid) was found to be a dominant CGA in C. asiatica cells, although the SA treatment also had a negative effect on its concentration. Overall SA treatment was found to be an ineffective elicitor of CGA production in cultured C. asiatica cells.