Development of a molecular marker based on chloroplast gene for specific identification of Korean Hibiscus (Hibiscus syriacus ‘Simbaek’)

Due to the rise in substitution and adulteration of herbal products, as well as the lack of genetic information on Hibiscus plants, more molecular markers are needed to understand the genetic diversity and avoid their misidentification. There are many allelic variants of the functional genes in Hibiscus and other plants, which control their respective phenotypes and other characteristics. Identifying alleles of the desired trait by determining diversification through gene-typing allele-specific markers for authentication is, therefore, a potent strategy. The purpose of this study was to use insertion/deletion (InDel) markers to identify Hibiscus syriacus cultivars. We developed a novel InDel marker for Korean Hibiscus ‘Simbaek’, based on the trnL-F region of the chloroplast gene. Through this InDel site, a modified specific primer pair and a novel multiplex polymerase chain reaction (PCR) system were developed for specific identification of the Korean Hibiscus Simbaek cultivar. The molecular markers developed in this study were highly specific and accurately authenticated as Simbaek from the five main cultivars of H. syriacus. Taken together, the described method is a potential tool for the identification and selection of germplasm resource of Simbaek cultivar. Graphical Abstract

Physicochemical Characterization and Antimicrobial Activity against Erwinia amylovora, Erwinia vitivora, and Diplodia seriata of a Light Purple Hibiscus syriacus L. Cultivar

Phytochemicals are essential raw materials for the production of formulations that can be helpful in crop protection. In particular, Hibiscus spp., which are often used in traditional medicine, are rich in potential bioactive molecules. This study presents an analysis of the thermal, vibrational, and phytochemical characteristics of a light purple variety of Hibiscus syriacus, using thermal gravimetric and differential scanning calorimetry, Fourier-transform infrared spectroscopy, and gas chromatography-mass spectroscopy techniques. Further, with a view to its valorization, the antimicrobial activity of its extracts has been investigated in vitro against Erwinia amylovora (the phytopathogen responsible for fire blight in apples, pears, and some other members of the family Rosaceae), Erwinia vitivora (the causal agent of the “maladie d’Oléron” in grapevines), and Diplodia seriata (responsible for “Bot canker”). Higher heating values and thermal features showed similarities with kenaf biomass. The main compounds identified in the hydro-methanolic extracts were: in flowers, 1-heptacosanol, heptacosane, 1-tetracosanol, hexadecenoic acid, 9,12,15-octadecatrienoic acid, and 9,12-octadecadienoic acid; and in leaves, the coumarin derivative 4,4,6,8-tetramethyl-2-chromanone, vitamin E, phytol, and sitosterol. MIC values of 500 and 375 μg·mL−1 were obtained against E. amylovora for flower and leaf extracts, respectively, upon conjugation with chitosan oligomers (to improve solubility and bioavailability). In the case of E. vitivora, MIC values of 250 and 500 μg·mL−1, respectively, were registered. Regarding the antifungal activity, EC90 values of 975.8 and 603.5 μg·mL−1, respectively, were found. These findings suggest that H. syriacus (cv. ‘Mathilde’) may be a promising source of antimicrobials for agriculture.

Anthocyanins from Hibiscus syriacus L. Inhibit NLRP3 Inflammasome in BV2 Microglia Cells by Alleviating NF-κB- and ER Stress-Induced Ca2+ Accumulation and Mitochondrial ROS Production

Anthocyanins from the petals of Hibiscus syriacus L. (PS) possess anti-inflammatory, antioxidant, and antimelanogenic activities. However, it remains unclear whether PS inhibit the NLR family pyrin domain-containing 3 (NLRP3) inflammasome activation and assembly. This study is aimed at investigating whether PS downregulate NLRP3-mediated inflammasome by inhibiting nuclear factor-κB (NF-κB) and endoplasmic reticulum (ER) stress. BV2 microglia cells were treated with PS in the presence of lipopolysaccharide and adenosine triphosphate (LPS/ATP), and the NLRP3-related signaling pathway was investigated. In this study, we found that LPS/ATP treatment activated the NLRP3 inflammasome, which resulted in the release of interleukin-1β (IL-1β) and IL-18. Meanwhile, PS reduced LPS/ATP-mediated NLRP3 inflammasome at 12 h by inhibiting ER stress-mediated Ca2+ accumulation and subsequent mitochondrial reactive oxygen species (mtROS) production, which, in turn, decreased IL-1β and IL-18 release. Furthermore, PS inhibited the NLRP3 inflammasome 1 h after LPS/ATP treatment by suppressing the NF-κB pathway, which downregulated Ca2+ accumulation and mtROS production. These data showed that PS negatively regulated activation of the NLRP3 inflammasome in a time-different manner by inhibiting the NF-κB signaling pathway in the early stage and the ER stress response in the late stage. The pathways shared Ca2+ accumulation-mediated mtROS production, which was significantly inhibited in the presence of PS. In conclusion, our results suggested that PS has potential as a supplement against NLRP3 inflammasome-related inflammatory disorders; nevertheless, further studies are needed to determine the effect of PS in the noncanonical NLRP3 inflammasome pathways and pathological conditions in vivo.