The alkaloid 1-deoxynojirimycin (DNJ) is the main bioactive ingredient in the hypoglycemic action of mulberry leaves (Morus alba L.). Our previous research clarified the upstream pathway from lysine to Δ1-piperideine in the biosynthesis of DNJ in mulberry leaves, but the pathway and related reductase genes from Δ1-piperideine to piperidine are still unclear. Here, a comparative transcriptome was used to analyze the transcriptome data of two samples (July and November) of mulberry leaves with significant differences in the content of DNJ and screen-related reductase genes. Results showed that expression levels of MaSDR1 and MaSDR2 were significantly and positively correlated with the content of DNJ (P < 0.05) in different seasons. MaSDR1 (GenBank accession no. MT989445) and MaSDR2 (GenBank accession no. MT989446) were successfully cloned and used for prokaryotic expression and functional analysis in vitro. MaSDR1 and MaSDR2 could catalyze the reaction of Δ1-piperideine with the coenzyme NADPH to generate piperidine. The kinetic parameters of MaSDR1 and MaSDR2 indicated that MaSDR2 had a higher binding ability to Δ1-piperideine than MaSDR1. This study provided insights into the biosynthesis of DNJ in mulberry leaves.

Dendrobium huoshanense is a Chinese medicinal herb that has high quality and excellent efficacy. However, the chemical basis of its activity is still unclear. Of note, Dendrobium officinale is the most widely utilized among the Dendrobium species. Therefore, the current study systematically investigated the chemical constituents of methanolic extracts and different polar fractions of aqueous extracts from the two herbs by HPLC–ESI–MSn, and then compared in vitro antioxidant activities of their five different polar extracts. Consequently, 61 and 49 compounds were identified from D. huoshanense and D. officinale, respectively, of which 43 compounds were common to both species. In addition, 17 out of 22 different compounds were identified only in D. huoshanense. Moreover, the peak areas of some shared identical compounds of D. huoshanense were significantly larger than that of D. officinale. In vitro antioxidant evaluation results showed that the n‐BuOH‐soluble fraction of the two herbs exhibited remarkable antioxidant activities. Furthermore, the antioxidant activities of different fractions of D. huoshanense were separately superior to that of D. officinale, which may be attributed to its variable and high contents of flavonoids, bibenzyls and phenanthrenes. These results provide the evidence for the high quality and efficacy of D. huoshanense.

Background The main active ingredients of Mentha haplocalyx Briq. essential oils are monoterpenes. According to the component of essential oils, M. haplocalyx can be divided into different chemotypes. Chemotype variation is widespread in Mentha plants but its formation mechanism is unclear. Methods We selected the stable chemotype l-menthol, pulegone, and carvone of M. haplocalyx for transcriptome sequencing. To further investigate the variation of chemotypes, we analyzed the correlation between differential transcription factors (TFs) and key enzymes. Results Fourteen unigenes related to monoterpenoid biosynthesis were identified, among which (+)-pulegone reductase (PR) and (−)-menthol dehydrogenase (MD) were significantly upregulated in l-menthol chemotype and (−)-limonene 6-hydroxylase was significantly upregulated in carvone chemotype. In addition, 2,599 TFs from 66 families were identified from transcriptome data and the differential TFs included 113 TFs from 34 families. The families of bHLH, bZIP, AP2/ERF, MYB, and WRKY were highly correlated with the key enzymes PR, MD, and (−)-limonene 3-hydroxylase (L3OH) in different M. haplocalyx chemotypes (r > 0.85). The results indicate that these TFs regulate the variation of different chemotypes by regulating the expression patterns of PR, MD, and L3OH. The results of this study provide a basis for revealing the molecular mechanism of the formation of different chemotypes and offer strategies for effective breeding and metabolic engineering of different chemotypes in M. haplocalyx.

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Background: Dendrobium huoshanense C. Z. Tang et S. J. Cheng (D. huoshanense) is a precious Dao-di herb with high quality, excellent efficacy and edible value of China, Dendrobium officinale Kimura et Migo (D. officinale) is widely utilized and commonly used as a substitute for D. huoshanense. But few studies have been conducted to systematically analyze chemical composition and bioactivities of the two.Methods: HPLC-ESI-MSn was used to identify the compounds in D. huoshanense and D. officinale grown in Huoshan from methanol extracts and different polar fractions of water extracts, including petroleum ether, ethyl acetate and n-butanol; The in vitro antioxidant activity were evaluated by the scavenging effects on DPPH and ·OH radicals, total reduction ability and total antioxidant ability.Results: 61 compounds were identified in D. huoshanense and 49 compounds were identified in D. officinale and with 43 shared compounds; Among them, 44 and 7 compounds were respectively identified from the two for the first time. Oxyresveratrol, quercetin-3-O-glucoside, quercetin-3-O-arabinoside, naringenin-7-O-glucoside, baicalin, hesperetin, vitexin and apigenin-6-C-pentosyl-8-C-(2’’-O-quinoyl)-glucoside were first identified in Dendrobium. In addition, 5 compounds were unique in D. huoshanense compared with other species of Dendrobium . The results of in vitro antioxidant activity showed that n-BuOH-soluble fraction of D. huoshanense and D. officinale both revealed the strongest antioxidant activities compared with other fractions, furthermore, the antioxidant activities of different fractions of D. huoshanense were separately superior to that of D. officinale.Conclusion: These results may provide a reference for the substances study about D. huoshanense's high-quality efficacy, and also provide a scientific basis for its development and utilization.