Differentiation of Three Centella Species in Australia as Inferred from Morphological Characteristics, ISSR Molecular Fingerprinting and Phytochemical Composition

Comprehensive analysis using DNA metabarcoding, SCAR marker based PCR assay, and HPLC unveils the adulteration in Brahmi herbal products

BACKGROUND

Brahmi is one of the important nootropic botanicals, widely sold in the market, with the name "Brahmi'' being used to describe both Bacopa monnieri and Centella asiatica species. The Brahmi herbal products market is expanding; hence, economically motivated adulteration is highly prevalent.

METHODS AND RESULTS

This study aimed to develop DNA-based methods, including SCAR marker-based PCR and metabarcoding, to authenticate Brahmi herbal products and compare these methods with HPLC. These methods have been validated using mock controls (in-house blended formulations). All targeted plant species in mock controls were detected successfully with all three methods, whereas, in market samples, only 22.2%, 55.6%, and 50.0% were found positive for Brahmi by PCR assay, DNA metabarcoding, and HPLC, respectively. Metabarcoding can detect the presence of non-labeled plants together with targeted species, which is an advantage over PCR assay or HPLC.

CONCLUSION

SCAR marker-based PCR is a rapid and cost-effective method for detecting the presence of B. monnieri and C. asiatica. However, in this study, the success rate of PCR amplification was relatively low because the primers targeted either RAPD or ITS-based SCAR markers. HPLC assay, although an alternative, was unable to detect the presence of other botanicals, just like the SCAR marker-based PCR assay. On the other hand, metabarcoding can be utilized to identify the target plants, even in very small quantities, while also providing simulated identification of other botanicals. This study successfully addressed the need for quality control of Brahmi herbal products and provided the first-time report of DNA metabarcoding for such products.

Morphological Description and Ethnobotanical Review of the Orphan Crop Myin-Hkwa (Centella asiatica L.) From Myanmar

Centella asiatica is a medicinal herb commonly known as Asiatic pennywort or gotu kola. The species is valued for its medicinal and nutritional properties. It is a perennial plant with leaves and stems that can be consumed as a green leafy vegetable. It is used as a folk remedy to cure various mild and chronic diseases due to its anti-rheumatic, antipyretic, antibacterial, antiviral, and anti-inflammatory effects, and as a mental rejuvenator. Although the species is widely distributed throughout the tropics and subtropics, its recognition was limited. The morphological description of C. asiatica is not well-documented in Myanmar, in Burmese or other local languages. Plant assessment via morphological markers is one of the ultimate methods for the primary description and characterization of their phenotypic traits. The objectives of this study were focused on the description of Myanmarese C. asiatica grown in Japan through morphological markers and a brief overview of its ethnobotanical use in Asia. Morphological characterization revealed the quantitative and qualitative differences regarding several traits among assessed C. asiatica samples. Furthermore, the study can provide information on the primary C. asiatica cultivation system in Japan, as it can be a potentially new and economically important crop for the Japanese market.

Genetic diversity and structure revealed by genomic microsatellite markers in Centella asiatica (L.) Urb., a plant with medicinal potential

BACKGROUND

Around the world, medicinal plants are utilised for various purposes. Centella asiatica is one of the important medicinal plants widely used in many medicinal systems. Nevertheless, analysis of the genetic diversity would pave the way for its most suitable utilisation.

METHODS AND RESULTS

The present study analyses the genetic diversity and structure of eighty C. asiatica accessions collected from the southern states of India, using ten genomic microsatellite markers. The mean Nei's gene diversity (0.46) indicates considerable genetic diversity. Analysis of molecular variance (82.48%) exhibited significant genetic variance between samples within the population. The cluster analysis brought out the structure of the analysed populations as three subpopulations based on the genetic differentiation.

CONCLUSIONS

The study showed significant intra-population variation, predominant inbreeding and population differentiation in C. asiatica. The findings will help better understanding of the genetic structure and gene pool of the plant.

De novo chromosome-level assembly of the Centella asiatica genome

Centella asiatica is a herbaceous, perennial species indigenous to India and Southeast Asia. C. asiatica possesses several medicinal properties: anti-aging, anti-inflammatory, wound healing and memory enhancing. The lack of available genomics resources significantly impedes the improvement of C. asiatica varieties through molecular breeding. Here, we combined the 10× Genomics linked-read technology and the long-range HiC technique to obtain the genome assembly. The final assembly contained nine pseudomolecules, corresponding to the haploid chromosome number in C. asiatica. These nine chromosomes covered 402,536,584 bases or 93.6% of the 430-Mb assembly. Comparative genomics analyses based on single-copy orthologous genes showed that C. asiatica and the common ancestor of Coriandrum sativum (coriander) and Daucus carota (carrot) diverged about 48 million years ago. This assembly provides a valuable reference genome for future molecular studies, varietal development through marker-assisted breeding and comparative genomics studies in C. asiatica.

Attenuation of methylglyoxal-induced glycation and cellular dysfunction in wound healing by Centella cordifolia

Current pre-clinical evidences of Centella focus on its pharmacological effects on normal wound healing but there are limited studies on the bioactivity of Centella in cellular dysfunction associated with diabetic wounds. Hence we planned to examine the potential of Centella cordifolia in inhibiting methylglyoxal (MGO)-induced extracellular matrix (ECM) glycation and promoting the related cellular functions. A Cell-ECM adhesion assay examined the ECM glycation induced by MGO. Different cell types that contribute to the healing process (fibroblasts, keratinocytes and endothelial cells) were evaluated for their ability to adhere to the glycated ECM. Methanolic extract of Centella species was prepared and partitioned to yield different solvent fractions which were further analysed by high performance liquid chromatography equipped with photodiode array detector (HPLC-PDA) method. Based on the antioxidant [2,2-diphenyl-1-picrylhydrazyl (DPPH) assay] screening, anti-glycation activity and total phenolic content (TPC) of the different Centella species and fractions, the ethyl acetate fraction of C. cordifolia was selected for further investigating its ability to inhibit MGO-induced ECM glycation and promote cellular distribution and adhesion. Out of the three Centella species (C. asiatica, C. cordifolia and C. erecta), the methanolic extract of C. cordifolia showed maximum inhibition of Advanced glycation end products (AGE) fluorescence (20.20 ± 4.69 %, 25.00 ± 3.58 % and 16.18 ± 1.40 %, respectively). Its ethyl acetate fraction was enriched with phenolic compounds (3.91 ± 0.12 mg CAE/μg fraction) and showed strong antioxidant (59.95 ± 7.18 μM TE/μg fraction) and antiglycation activities. Improvement of cells spreading and adhesion of endothelial cells, fibroblasts and keratinocytes was observed for ethyl acetate treated MGO-glycated extracellular matrix. Significant reduction in attachment capacity of EA.hy926 cells seeded on MGO-glycated fibronectin (41.2%) and attachment reduction of NIH3t3 and HaCaT cells seeded on MGO-glycated collagen (33.7% and 24.1%, respectively) were observed. Our findings demonstrate that ethyl acetate fraction of C. cordifolia was effective in attenuating MGO-induced glycation and cellular dysfunction in the in-vitro wound healing models suggesting that C. cordifolia could be a potential candidate for diabetic wound healing. It could be subjected for further isolation of new phytoconstituents having potential diabetic wound healing properties.