Site-Selective and Biocompatible Growth of Polymers from Glycan Moieties of Glycoproteins and Living Cells.

Formation of protein-polymer conjugates (PPCs) is critical for many studies in chemical biology, biomedicine, and enzymatic catalysis. Polymers with coordinated physicochemical properties confer synergistic functions to PPCs that overcome the inherent limitation of proteins. However, application of PPCs has been synthetically restricted by the limited modification sites and polymer grafting method. Here, we present a versatile strategy for site-selective PPC synthesis. The initiator was specifically tethered to the preoxidized glycan moieties through oxime chemistry. Polymer brushes were grown in situ from the glycan by atom-transfer radical polymerization to generate well-controlled PPCs. Notably, the modification is site-specific, multivalent, and alterable depending on protein glycosylation. Additionally, we demonstrated that the cytocompatible method enabled the growth of polymer chains from the surface of living yeast cells. These results verified a facile technology for surface modification of biomacromolecules by desired polymers for various biomedical applications.

Oxidation of Cucurbitadienol Catalyzed by CYP87D18 in the Biosynthesis of Mogrosides from Siraitia grosvenorii.

Mogrosides, the principally bioactive compounds extracted from the fruits of Siraitia grosvenorii, are a group of glycosylated cucurbitane-type tetracyclic triterpenoid saponins that exhibit a wide range of notable biological activities and are commercially available worldwide as natural sweeteners. The biosynthesis of mogrosides involves initial cyclization of 2,3-oxidosqualene to the triterpenoid skeleton of cucurbitadienol, followed by a series of oxidation reactions catalyzed by Cyt P450s (P450s) and then glycosylation reactions catalyzed by UDP glycosyltransferases (UGTs). We previously reported the identification of a cucurbitadienol synthase (SgCbQ) and a mogrol C-3 hydroxyl glycosyltransferase (UGT74AC1). However, molecular characterization of further transformation of cucurbitadienol to mogrol by P450s remains unavailable. In this study, we report the successful identification of a multifunctional P450 (CYP87D18) as being involved in C-11 oxidation of cucurbitadienol. In vitro enzymatic activity assays showed that CYP87D18 catalyzed the oxidation of cucurbitadienol at C-11 to produce 11-oxo cucurbitadienol and 11-hydroxy cucurbitadienol. Furthermore, 11-oxo-24,25-epoxy cucurbitadienol as well as 11-oxo cucurbitadienol and 11-hydroxy cucurbitadienol were produced when CYP87D18 was co-expressed with SgCbQ in genetic yeast, and their structures were confirmed by liquid chromatography-solid-phase extraction-nuclear magnetic resonance-mass spectrometry coupling (LC-SPE-NMR-MS). Taken together, these results suggest a role for CYP87D18 as a multifunctional cucurbitadienol oxidase in the mogrosides pathway.

Functional Characterization of Cucurbitadienol Synthase and Triterpene Glycosyltransferase Involved in Biosynthesis of Mogrosides from Siraitia grosvenorii.

Mogrosides, the major bioactive components isolated from the fruits of Siraitia grosvenorii, are a family of cucurbitane-type tetracyclic triterpenoid saponins that are used worldwide as high-potency sweeteners and possess a variety of notable pharmacological activities. Mogrosides are synthesized from 2,3-oxidosqualene via a series of reactions catalyzed by cucurbitadienol synthase (CbQ), Cyt P450s (P450s) and UDP glycosyltransferases (UGTs) in vivo. However, the relevant genes have not been characterized to date. In this study, we report successful identification of SgCbQ and UGT74AC1, which were previously predicted via RNA-sequencing (RNA-seq) and digital gene expression (DGE) profile analysis of the fruits of S. grosvenorii. SgCbQ was functionally characterized by expression in the lanosterol synthase-deficient yeast strain GIL77 and was found to accumulate cucurbitadienol as the sole product. UGT74AC1 was heterologously expressed in Escherichia coli as a His-tag protein and it showed specificity for mogrol by transfer of a glucose moiety to the C-3 hydroxyl to form mogroside IE by in vitro enzymatic activity assays. This study reports the identification of CbQ and glycosyltransferase from S. grosvenorii for the first time. The results also suggest that RNA-seq, combined with DGE profile analysis, is a promising approach for discovery of candidate genes involved in biosynthesis of triterpene saponins.

Qualitative and quantitative chemical analysis of Leptadenia hastata: exploring a traditional african medicinal plant.

Leptadenia hastata (Pers.) Decne is a commonly used food source and prescribed as a traditional African medicine for treatment of various diseases, such as diabetes, skin disorders, wounds, and ulcers. However, quality control has become a bottleneck restricting the therapeutic development and utilization of this plant. In this study, a reliable method for qualitative and quantitative determination of components in Leptadenia hastata was established. The components of L. hastata were profiled using ultra-high performance liquid chromatography coupled with quadruple time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS). Subsequently, an ultra-high performance tandem diode array detector (UHPLC-DAD)-based method was used for simultaneous quantitative analysis of five major constituents in six batches of L. hastata samples. As a result, 35 compounds were tentatively identified. The quantities of the five constituents (vicenin-Ⅱ, orientin, schaftoside, chrysin 6-C-arabinoside 8-C-glucoside, chrysin 6-C-glucoside 8-C-arabinoside) were determined as 124.8-156.9 µg/g, 170.5-216.0 µg/g, 61.31-93.73 µg/g, 85.13-119.3 µg/g and 99.82-129.4 µg/g, respectively. This method offers a successful strategy for precise and effective evaluation of the constituents of L. hastata, providing a robust foundation for holistic quality assessment of medicinal plants.

Phytochemicals-based investigation of Rubia cordifolia pharmacological potential against letrozole-induced polycystic ovarian syndrome in female adult rats: In vitro, in vivo and mechanistic approach.

Polycystic Ovarian Syndrome (PCOS) is a metabolic, reproductive, and endocrine disorder affecting women of fertile age. This study aimed to formulate a phytochemicals-based standardized aqueous ethanolic extract of Rubia cordifolia (SERC) to explore its pharmacological potential in PCOS-induced female rats and elucidate its mechanism. HPLC analysis revealed the presence of phytochemicals such as chlorogenic acid, p-coumaric acid, gallic acid, and kaempferol. Thirty female adult rats were divided into two groups for induction of PCOS (5 female rats in the normal control group + 25 female rats in the disease-induced group). PCOS was induced by administering letrozole (1 mg/kg p.o.) for 6 weeks. After PCOS induction, animals of the disease-induced group were divided into five groups: one group used as disease control (PCOS) group, one group on metformin (20 mg/kg), and three groups on SERC (200, 400, and 600 mg/kg). Histopathological analysis showed that PCOS induction reduced corpus luteum and developing follicles and increased cystic follicles. In comparison, SERC treatment improved ovulation with more primary and developing follicles. SERC reduced the serum insulin, LH surge, and testosterone levels while improving the FSH, estrogen, and progesterone serum levels. SERC significantly improved the oxidation status of the liver and normalized the lipid profile and liver function markers. In conclusion, SERC treated PCOS, and the suggested mechanism might be the restoration of aromatase activity and background inflammatory status improvement in ovaries.

Free radical scavenging activity and characterization of sesquiterpenoids in four species of Curcuma using a TLC bioautography assay and GC-MS analysis.

The sesquiterpenoids are one of major groups of antioxidants in Curcuma besides curcuminoids. However, the real substances contributing to the antioxidant activity are still unknown. In this paper, the antioxidant activity of sesquiterpenoids in four species and two essential oils from Curcuma genus was determined and compared based on TLC separation and DPPH bioautography assay. Their antioxidant capacities were quantitatively evaluated using densitometry with detection at 530 nm (λ(reference )= 800 nm) using vitamin C as reference. The results showed that Curcuma longa rhizomes had the highest antioxidant capacity while C. phaeocaulis presented the lowest one among the four species of Curcuma. Moreover, essential oil of C. wenyujin showed higher antioxidant potential than that of C. longa. The main TLC bands with antioxidant activity of the four species of Curcuma were collected and characterized using GC-MS, and thus curzerene, furanodiene, α-turmerone, ß-turmerone and ß-sesquiphellandrene were determined as major sesquiterpenoids with antioxidant activity in Curcuma.