Medicinal plants play important roles in traditional medicine, and numerous compounds among them have been recognized for their antimicrobial activity. However, little is known about the potential of Vietnamese medicinal plants for antifungal activity. In this study, we examined the antagonistic activity of twelve medicinal plant species collected in Northern Vietnam against Penicillium digitatum, Aspergillus flavus, Aspergillus fumigatus, and Candida albicans. The results showed that the antifungal activities of the crude extracts from Mahonia bealei, Ficus semicordata, and Gnetum montanum were clearly detected with the citrus postharvest pathogen P. digitatum. These extracts could fully inhibit the growth of P. digitatum on the agar medium, and on the infected citrus fruits at concentrations of 300–1000 µg/mL. Meanwhile, the other tested fungi were less sensitive to the antagonistic activity of the plant extracts. In particular, we found that the ethanolic extract of M. bealei displayed a broad-spectrum antifungal activity against all four pathogenic fungi. Analysis of this crude extract by enrichment coupled with high-performance liquid chromatography revealed that berberine and palmatine are major metabolites. Additional inspections indicated berberine as the key compound responsible for the antifungal activity of the M. bealei ethanolic extract. Our study provides a better understanding of the potential of Vietnamese medicinal plant resources for combating fungal pathogens. This work also highlights that the citrus pathogen P. digitatum can be employed as a model fungus for screening the antifungal activity of botanicals.

The medicinal mushroom Cordyceps militaris is widely exploited in traditional medicine and nutraceuticals in Asian countries. However, fruiting body production in C. militaris is facing degeneration through cultivation batches, and the molecular mechanism of this phenomenon remains unclear. This study showed that fruiting body formation in three different C. militaris strains, namely G12, B12, and HQ1, severely declined after three successive culturing generations using the spore isolation method. PCR analyses revealed that these strains exist as heterokaryons and possess both the mating-type loci, MAT1-1 and MAT1-2. Further, monokaryotic isolates carrying MAT1-1 or MAT1-2 were successfully separated from the fruiting bodies of all three heterokaryotic strains. A spore combination of the MAT1-1 monokaryotic isolate and the MAT1-2 monokaryotic isolate promoted fruiting body formation, while the single monokaryotic isolates could not do that themselves. Notably, we found that changes in ratios of the MAT1-2 spores strongly influenced fruiting body formation in these strains. When the ratios of the MAT1-2 spores increased to more than 15 times compared to the MAT1-1 spores, the fruiting body formation decreased sharply. In contrast, when MAT1-1 spores were increased proportionally, fruiting body formation was only slightly reduced. Our study also proposes a new solution to mitigate the degeneration in the heterokaryotic C. militaris strains caused by successive culturing generations.

Cordyceps militaris is a valuable fungus that is well-known in many Asian countries. The fruiting bodies of C. militaris are commonly used in traditional medicine and the production of functional foods. Currently, C. militaris mushrooms are being cultivated on a large scale in Vietnam, yielding the characteristic yellow-orange fruiting bodies typical of C. militaris. In the mushroom cultivation industry, C. militaris is one of the most highly valued species. The yield and quality of the fruiting bodies are greatly dependant on the strain source. Therefore, the search for new strains of C. militaris with high productivity, quality, and uniqueness is always of interest to scientists. This study has isolated and identified the albino strain C. militaris SHBTD based on morphological characteristics and the rDNA ITS region gene sequence. The optimal conditions for fruiting body formation of the SHBTD strain are MT6 medium, a temperature of 22°C, a humidity of 90%, a light intensity of 500 lux (12 hours/day), and 65 days of cultivation. Additionally, this study determined that the albino strain C. militaris SHBDT carrying the single Mating-type (MAT) gene (MAT1-1-1), could provide stable yield and quality of fruiting bodies over 5 consecutive cultivation generations. The obtained results demonstrate the potential applications of the C. militaris SHBTD in the industrial-scale production of unique and high-value mushroom products.

Soapnuts represent a promising natural source of surface-active compounds for the development of eco-friendly bio-detergents as alternatives to conventional chemical-based cleaning products. Currently, soapnuts are recognized as a major saponin-rich raw material for producing various bio-based cleansing products such as shampoos, soaps, body washes, and dishwashing liquids. Soapnut extracts, which are rich in saponins, have been demonstrated to exhibit multiple biological activities, including anticancer, antifungal, antibacterial, and anti-inflammatory effects. Moreover, saponins from soapnuts also show strong cleansing properties. These characteristics make soapnuts a promising raw material for the development of green detergent products that are safer for human health. This study aimed to optimize several parameters in the fermentation process of soapnuts using Saccharomyces cerevisiae, employing response surface methodology (RSM) to obtain a fermented extract with the highest possible saponin-to-total soluble solids (TSS) ratio. The multi-factor experimental plan employed the Box-Behnken planning model with three independent variables corresponding to the following variation ranges: inoculum size (1-15%), fermentation temperature (25-35ºC), and fermentation time (2-8 days), with the objective function being the saponin/TSS content (%). Experimental results revealed that the optimal conditions for achieving the highest saponin/TSS content (85.1%) were an inoculum size of 9%, a fermentation temperature of 32°C, and a fermentation duration of 5 days. The fermented extract exhibited strong antibacterial activity against three pathogenic bacterial strains: Escherichia coli VTCC12272, Bacillus cereus SH46, and Staphylococcus aureus VTCC12275, with mean inhibition zone diameters of 20.5, 15.3, and 28.2 mm, respectively. The fermented extract from soapnut exhibited a high saponin/TSS content. It demonstrated significant antimicrobial activity, indicating its strong potential as a valuable raw material for the development of natural bio-detergent products.