The complete chloroplast genome sequence of Calystegia hederacea Wall. in Roxb. 1824 (Convolvulaceae) in Enshi, Hubei.

Calystegia hederacea Wall. in Roxb. 1824 is a perennial herbaceous vine in the family Convolvulaceae and has several biological effects. Herein, we reported the first complete chloroplast genome of C. hederacea. The chloroplast genome sequence was 152,057 bp in length, comparing a large single-copy (LSC) region of 87,891 bp, a small single-copy (SSC) region of 19,866 bp, and a pair of inverted repeat (IR) regions of 22,150 bp. This sequenced chloroplast genome contained 126 predicted genes, including 81 protein-coding genes, 37 tRNA genes, and eight rRNA genes, and the total GC content of the chloroplast genome was 37.79%. Phylogenetic analysis revealed that C. hederacea was closely related to C. soldanella. The chloroplast genome presented in this study will enrich the genome information of the genus Calystegia and provide deeper insights into the evolution study of the family Convolvulaceae.

Isolation and structural characterization of eight new resin glycosides, calyhedins XVI-XXIII, from the rhizomes of Calystegia hederacea.

Biological effects attributed to resin glycosides, including cytotoxicity against cancer cells and antibacterial, multidrug resistance-modulating, and antiviral activities have been documented. Penta-glycosides composed of calysolic acid A or calyhedic acid A, which are glycosidic acid components of the crude resin glycoside fraction of Calystegia hederacea, have not yet been isolated from this plant. In this study, eight new resin glycosides, termed calyhedins XVI (1)-XXIII (8), were isolated from the rhizomes of C. hederacea. Compounds 1-8 are penta- or hexa-glycosides with macrolactone structures, and their sugar moieties are partially acylated by five organic acids, including 2S-methylbutyric, (E)-2-methylbut-2-enoic, and 2R-methyl-3R-hydroxybutyric acids. Compounds 1-5 are the first identified macrocyclic resin glycosides with five monosaccharides obtained from this plant, and 2 and 4 are the first to be characterized as containing calyhedic acid A as the glycosidic acid component. Compounds 1-8 were of the four following macrolactone types: one with a 22-membered ring (5), another with a 23-membered ring (6-8), the third with a 27-membered ring (1, 3), and the fourth with a 28-membered ring (2, 4). Compounds 2-8 exhibited cytotoxic activity against HL-60 human promyelocytic leukemia cells comparable to that of the positive control, cisplatin.

Five new resin glycosides, calyhedins XI-XV, from Calystegia hederacea.

Calystegia hederacea Wall. (Convolvulaceae) is a perennial herbaceous vine that grows widely in India and East Asia. All parts of this plant are used to treat various disorders such as menoxenia and gonorrhea. Four new resin glycosides, calyhedins XI (1)-XIV (4), were isolated from the rhizomes of C. hederacea. A new glycoside, calyhedin XV (5), was isolated from its leaves and stems. Alkaline hydrolysis of 1 and 2 furnished a new glycosidic acid, calyhedic acid G (1a), from 1 and a new acid, calyhedic acid H (2a), from 2 along with 2S-methylbutyric acid and 2R-methyl-3R-hydroxybutyric (2R,3R-nilic) acid. The structures of 1-5, 1a, and 2a were determined using MS and NMR spectral analyses. Compounds 1a and 2a had the same sugar moiety, ß-D-glucopyranosyl-(1 → 6)-O-ß-D-glucopyranosyl-(1 → 6)-O-ß-D-glucopyranosyl-(1 → 3)-[O-ß-D-glucopyranosyl-(1 → 3)-O-α-L-rhamnopyranosyl-(1 → 2)]-O-ß-D-glucopyranosyl-(1 → 2)-ß-D-fucopyranose, while their aglycones were 11S-dihydroxyhexadecanoic acid and 12S-dihydroxyhexadecanoic acid, respectively. These compounds are the first glycosidic acids, with fucose as the monosaccharide component obtained from the resin glycosides of C. hederacea. Compounds 1-5, comprising either 1a or 2a, were heptaglycosides with macrolactone structures, and their sugar moieties were partially acylated with 5 mol of organic acids comprising 2S-methylbutyric, (E)-2-methylbut-2-enoic, and 2R,3R-nilic acids. Compounds 1 and 5 had 22-membered rings, while 2-4 had 28-membered rings. In addition, 1 and 5 exhibited cytotoxic activity against HL-60 human promyelocytic leukemia cells, comparable to that of the positive control cisplatin.

First Report of Calystegia hederacea as a new host of sweet potato leaf curl Hubei virus.

Calystegia hederacea (Convolvulaceae) is one of the most problematic perennial weeds widely distributed around or in crop fields. Our previous studies showed that C. hederacea is natural reservoir of sweet potato chlorotic stunt virus isolate CH (SPCSV-CH) and sweet potato latent virus (SPLV) (Liu et al. 2020; Zhao et al. 2022). To shed further light on the role of C. hederacea in the epidemiology of sweet potato viruses, in May 2021, a total of seven C. hederacea plants (five asymptomatic, one curling and one mild vein-clearing) were collected from two different sweet potato fields in Xinxiang city of Henan Province in China. Total RNA was prepared from a pool of the seven leaf samples using the EZNA Plant RNA Kit (Omega Bio-Tek, Norcross, GA). A library was constructed from the ribosomal-depleted RNA using the NEBNext Ultra Directional RNA Library Prep Kit for Illumina (NEB, MA, USA) and sequenced using the Illumina HiSeq platform (Novogene, Tianjin, China). A total of 139,057,020 paired-end clean reads of 150 bp were obtained after removing adaptor sequences and low-quality reads and used for de novo assembly using the Trinity (v2.2.0) software. Blast searches of the assembled contigs longer than 200 bp against NCBI nucleotide and protein sequence databases revealed the presence of 37 contigs (237 to 4885 bp) and 19 contigs (261 to 758 bp) with high nucleotide (nt) identity with SPLV and SPCSV-CH, respectively. The occurrence of SPLV and SPCSV-CH on C. hederacea was previously reported, and thus the contig sequences related to SPLV and SPCSV-CH were not subjected to further verification in this study. In addition, one contig (2,827 bp) with the highest nt sequence identity of 94.94% with sweet potato leaf curl Hubei virus (SPLCHbV, genus Begomovirus, family Geminiviridae, accession no. MK931304) was assembled from 16,592 reads, with average coverage depth of 740.5X. These results suggested the presence of SPLCHbV in C. hederacea. To further confirm the RNA sequencing result, each of the seven samples was tested by PCR using partially overlapping (italicized nucleotides) forward and reverse primers (SweeIn-F1, 5`-GGAGGAAGCTAAGTACGAGAATCAGTTAGAG-3`; SweeIn-R1, 5`-GCTTCCTCCTTGTGATTGTAAGTAACATGG-3`) that were designed based on the SPLCHbV-related contig for amplification of circular DNA viral genome (approximately 2.7 kb). Two symptomatic and three symptomless C. hederacea samples were SPLCHbV positive, indicating that virus-like symptoms of the two C. hederacea samples were probably not induced by SPLCHbV. Two of the five amplified products were completely sequenced and deposited to GenBank (accession nos. OQ551733 and OQ551734). Sequences analysis showed that the complete genome sequences of two SPLCHbV C. headrace isolates (2,763 nt and 2,761 nt) had 96.53% nt identity with each other and 95.92 to 97.70% nt identity with that of SPLCHbV isolate Shandong7-2017 (MK931304). In August 2021, fourteen C. hederacea plants (three symptomatic, 11 asymptomatic) collected from natural fields from Zhumadian and Pingdingshan cities in Henan Province, were tested by PCR using SweeIn-F1/R1 primers for SPLCHbV, showing that eight samples were SPLCHbV positive. SPLCHbV belongs to the sweepoviruses, a group of phylogenetically distinct begomoviruses infecting sweet potato, and was reported to infect sweet potato from many provinces of China (Wang et al., 2021). To the best of our knowledge, this is the first report of SPLCHbV infection in C. hederacea, which expands the natural host range of SPLCHbV.

Four new resin glycosides, calyhedins VII-X, from the rhizomes of Calystegia hederacea.

Four new resin glycosides with macrolactone structures (jalapins), namely, calyhedins VII (1)-X (4), were isolated from the rhizomes of Calystegia hederacea Wall. (Convolvulaceae). The structures of 1-4 were determined based on spectroscopic data. They were classified into three ring types: a 27-membered ring (1), a 22-membered ring (2, 3), and a 23-membered ring (4). Their sugar moieties were partially acylated using five organic acids, including (E)-2-methylbut-2-enoic acid, 2S-methylbutyric acid, and 2 R-methyl-3R-hydroxybutyric acid. Compound 4 was the first genuine resin glycoside with calyhedic acid F as the glycosidic acid component. Additionally, the cytotoxic activities of 1, 2, and 4 towards HL-60 human promyelocytic leukaemia cells were evaluated. All compounds demonstrated almost the same activity as the positive control, cisplatin.

Calyhedins I-VI: Resin glycosides from the rhizomes of Calystegia hederacea.

Six previously undescribed resin glycosides, calyhedins I-VI, were isolated from the rhizomes of Calystegia hederacea Wall., which are the first genuine resin glycosides isolated from C. hederacea. The structures of calyhedins I-VI were determined based on spectroscopic data and chemical evidence. All the compounds have macrolactone structures (jalapins), and their sugar moieties were partially acylated by five organic acids. Calyhedins I, II-V, and VI have 27-, 28-, and 23-membered rings, respectively, and calyhedins IV-VI are the first jalapins with a sugar chain consisting of seven monosaccharides. Additionally, the cytotoxic activity of calyhedins II and III toward HL-60 human promyelocytic leukemia cells was evaluated. Both compounds demonstrated almost the same activity as the positive control, cisplatin.

Identification and characterization of organic and glycosidic acids in crude resin glycoside fraction from Calystegia hederacea.

Resin glycosides are well known as the purgative ingredients, which are characteristic of convolvulaceous plants. Calystegia hederacea Wall. is a perennial herbaceous vine that is widespread throughout India and East Asia. All parts of this plant are used for the treatment of menoxenia, gonorrhea, etc. Alkaline hydrolysis of the crude resin glycoside fraction of the whole plants of C. hederacea yielded four new glycosidic acids, calyhedic acids A, B, C, and D, along with two known glycosidic acids, calysolic acids A and C, and three known organic acids, 2S-methylbutyric, tiglic, and 2R,3R-nilic acids. Their structures were characterized on the basis of spectroscopic data and chemical evidence. Calyhedic acids A, B, and D were penta-, hexa-, and hepta-glycosides of 12S-hydroxyhexadecanoic acid, respectively, and cayhedic acid C was an isomer of calyhedic acid D, in which the 12S-hydroxyhexadecanoyl residue of calyhedic acid D was replaced by a 11S-hydroxyhexadecanoyl residue. Additionally, cytotoxic activity toward HL-60 human promyelocytic leukemia cells of the crude resin glycoside fraction, the glycosidic acid fraction, calyhedic acid A, and calysolic acid A from C. hederacea was evaluated. Furthermore, to clarify the structure-activity relationship of resin glycosides, the activities of six genuine resin glycosides with calysolic acid A or calysolic acid C as the glycosidic acid, which were isolated from C. soldanella, were examined. Among them, the crude resin glycoside fraction and five genuine resin glycosides with macrolactone structures demonstrated clear cytotoxic activities, while the glycosidic acid fraction, calyhedric acid A, calysolic acid A, and a genuine non-macrolactone-type resin glycoside were either inactive or exhibited weaker activity than the tested macrolactone-type resin glycosides.