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In September 2017, vein clearing and yellowing symptoms resembling those caused by viruses were observed on leaves of Malva verticillata in Chungnam, Korea. Nucleic acids were extracted from leaves of five symptomatic plants and tested by reverse transcription polymerase chain reaction using four virus specific primer pairs including malva vein clearing virus (MVCV). Amplicons of the expected size (600 bp) were obtained from total RNA of all samples using the MVCV-specific primers. To confirm the presence of MVCV in symptomatic plants, the DNA fragments from three samples were purified, and directly sequenced. BLAST analysis revealed that it shared the highest nucleotide identity (99%) with a MVCV isolate from tomato (Mexico). The virus isolates obtained from the third re-inoculated Chenopodium was designated as Cm1-5. Tissue from Cm1, Cm3, and Cm5 isolates was mechanically sap inoculated into 23 indicator plants. Cm3 isolate induced chlorotic local and mosaic symptoms in Althaea rosea. Phylogenetic analysis based on coat protein gene of 19 MVCV isolates from 6 different countries and plant species, did not correlated with either the geographical origin of the isolates, or pathogenicity. To our knowledge, this study first reports the natural occurrence of MVCV on M. verticillata in Korea and characterization of three Korean isolates of MVCV.

Malva verticillata, also known as Chinese mallow, is an herbaceous plant with colorful flowers and has been used as a medicine for thousands of years. This study investigated this herb for potential antioxidant activity or an association with osteoblast differentiation. M. verticillate leaves were fermented with B. subtilis MV1 at 30 &deg, C for 7 days to enhance their biological activities. The resultant aqueous extract (MVW) and the fermented leaves (MVB) were measured for antioxidant and osteoblast differentiation. The results showed that the total phenolic, flavonoid, and antioxidant activity, as well as the osteoblast differentiation of the MVB increased (2 to 6 times) compared with those of the MVW. MVB induced phosphorylation of p38, extracellular signal-regulated kinase in C3H10T1/2 cells, and the phosphorylation was attenuated via transforming growth factor-&beta, (TGF-&beta, ) inhibitors. Moreover, runt-related transcription factor 2 and osterix in the nucleus increased in a time-dependent manner. The messenger RNA expression of alkaline phosphatase and bone sialoprotein increased about 9.4- and 65-fold, respectively, compared to the non-treated cells. MVB stimulated C3H10T1/2 cells in the osteoblasts via TGF-&beta, signaling. Thus, fermented M. verticillata extract exhibited enhanced antioxidant activity and osteoblast differentiation.

A preliminary study revealed that a 10 µg/mL n-BuOH fraction of Malva verticillata aerial parts significantly enhanced splenocyte proliferation and induced significant enhancement of natural-killer (NK) cell activity against tumor cells (YAC-1). This study was initiated to identify the principal components that exhibited these activities, and four glycerides were isolated through repeated SiO2 and ODS column chromatography. Structures of compounds 1–4 were determined to be (2S)-1-O-palmitoyl glyceride, (2S)-1-O-stearoyl glyceride, (2S)-1-O-linolenoyl glyceride, and (2S)-1,2-di-O-linoleoyl glyceride, respectively. Compounds 1–3 showed potential immune-enhancing activity in murine splenocyte and natural-killer (NK) cells at 10 µM. In contrast, compound 4 showed weak activity, indicating the monoacyl glycerides (1–3) are more effective than diacyl glyceride (4). Also, the longer the carbon number of the fatty acid in monoacyl glyceride, the better the activity, and the monoacyl glyceride including an unsaturated fatty acid (3) is more effective than the glycerides including the saturated fatty acids (1–2).

Stimulation of AMP-activated protein kinase (AMPK) signaling followed by increase of glucose uptake in L6 myotubes were studied with organic solvent extract of Malva verticillata (MV) seeds. Ethanol extract of M. verticillata seeds (MVE) significantly increased the phosphorylation level of AMPK, acetyl-CoA carboxylase (ACC), and glucose uptake in L6 myotube cells. The MVE was fractionated with n-hexane (MVE-H), chloroform (MVE-C), ethylacetate (MVE-E), n-butanol (MVE-B), and water (MVE-W). MVE-H (150 microgram/ml) showed the highest phosphorylating activity and increased glucose uptake by 2.3-fold. Oral administration of MVE-H (40 mg/kg) for 4 weeks to type 2 diabetic (db/db) mice reduced non-fasting and fasting blood glucose levels by 17.1% and 23.3%, respectively. Phosphorylation levels of AMPK and ACC in the soleus muscle and liver tissue of db/db mice were significantly increased by the administration of MVE-H. MVE-H was further fractionated using preparative HPLC to identify the AMPK-activating compounds. The NMR and GC-MS analyses revealed that β-sitosterol was a major effective compound in MVE-H. Phosphorylation levels of AMPK and ACC, and glucose uptake were significantly increased by the treatment of MVE-S (β-sitosterol) isolated from M. verticillata to L6 cells, and these effects were attenuated by an AMPK inhibitor (Compound C) pretreatment. These results, taken together, demonstrate that increased glucose uptake in L6 myotubes by MVE-H treatment is mainly accomplished through the activation of AMPK. Our finding suggests that the extract isolated from M. verticillata seed would be beneficial for the treatment of metabolic disease including type 2 diabetes and hyperlipidemia.

Malva verticillata (Cluster mallow), a leafy vegetable that has been popular in East Asia for a long time, has also been used in herbal teas and medicines. The aqueous fraction of the aerial parts of Malva verticillata, exhibiting a very high quantity of flavonoids compared to the EtOAc and n-BuOH fractions, exhibited significant recovery effects on pancreatic islets damaged by alloxan in zebrafish larvae. Thus, the bioactive components responsible for this anti-diabetic activity were investigated. A new flavonoid glucuronide (1) and five known flavonoids were isolated from the aqueous fraction. Based on several spectroscopic methods, compound 1 was identified to be nortangeretin-8-O-β-d-glucuronide, and was named malvaflavone A. The A-ring of compound 1 had a 5,6,7,8-tetrahydroxy moiety, which rarely occurs in plant systems. Also 8-O-glucuronide attached to the flavonoid moiety was rarely occurred in plant system. Compounds 1, 3, 4, and 6 significantly improved the pancreatic islet size in zebrafish at 0.1 μM, and compounds 1 and 6 were found to block β-cell K+ channels in experiments with diazoxide. In ABTS, ORAC, and SOD assays, compounds 1–5 exhibited high anti-oxidant activities compared with quercetin and BHA (positive controls), indicating that the 8-O-glucuronide attached to the flavonoid moiety is a key structure for the expression of anti-oxidant activity. This is the first report of the isolation of compounds 1–6 from M. verticillata as well evaluated for anti-diabetic and anti-oxidant ativities.

An acidic polysaccharide, designated as MVS-IVA, was isolated from the seeds of Malva verticillata. It showed a remarkable reticuloendothelial system potentiating activity in the carbon clearance test. Chemical and spectroscopic studies demonstrated that the polysaccharide is rich in alpha-L-arabinofuranose residues and possesses mainly an alpha-1,5-linked L-arabino-beta-3,6-branched-D-galactan structure accompanied with rhamnogalacturonan type units. Both alpha-1,3-linked L-arabinopyranose and beta-1,4-linked D-xylopyranose residues were also identified as component units. MVS-IVA contains a small amount of protein (3.3%).

The controlled Smith degradation of MVS-VI, the major acidic polysaccharide having remarkable anti-complementary activity isolated from the seeds of Malva verticillata L., was performed. Methylation analysis of both the primary and the secondary Smith degradation products indicated that the core structural features of MVS-VI include a backbone chain composed of beta-1,3-linked D-galactose residues. The majority of galactose units in the backbone carry side chains composed of beta-1,3- and beta-1,6-linked D-galactosyl residues at position 6. The controlled Smith degradation products showed considerable anti-complementary activity.

Seven polysaccharides and peptidoglycans obtained from the seeds of Malva verticillata were tested for anti-complementary activity. Remarkable activities were observed for MVS-I and MVS-IIA. The former is mainly composed of beta-1,3-linked D-glucan and of alpha-1,5-linked L-arabino-beta-3,6-branched D-galactan, and the latter is essentially alpha-1,5-linked L-arabino-beta-3,6-branched D-galactan. Further, considerable activities were observed for MVS-IIIA and MVS-IVA. Both glycans possess arabino-3,6-galactan moieties accompanying alpha-1,3-linked L-arabinopyranosyl, beta-1,4-linked D-xylosyl, and alpha-1,4-linked D-galacturonic acid units. In addition, the major neutral polysaccharide (MVS-I), the major peptidoglycan (MVS-V), and the polysaccharide-rich fraction (MVS-V-CH) obtained from MVS-V were tested for hypoglycemic activity. MVS-I especially showed remarkable activity, and MVS-V-CH also exhibited significant activity. From the viewpoint of structural features, the latter belongs to pectic substances.

A novel acidic polysaccharide, designated as MVS-VI, was isolated from the seeds of Malva verticillata L. It was homogeneous on electrophoresis and gel chromatography, and its molecular mass was estimated to be 26000. It is composed of L-arabinose : D-xylose : D-galactose : D-glucose : L-rhamnose : D-galacturonic acid in the molar ratio of 30 : 15 : 20 : 3 : 2 : 10, in addition to small amounts of peptide moiety. Methylation analysis, carbon-13 nuclear magnetic resonance and periodate oxidation studies indicated its structural features to have mainly acidic α-arabino-3, 6-β-galactan type structural units. MVS-VI showed significant reticuloendothelial system-potentiating activity in a carbon clearance test, and it possesses remarkable anti-complementary activity.

From the hot water extract of the seeds of Malva verticillata , a polysaccharide (MVS-IIIA) has been isolated by fractionation on DEAE-Sephadex A-25 followed by chromatography on Sephacryl S-500 and Con A-Sepharose columns. Chemical and spectroscopic studies established that the polysaccharide possesses mainly an α-1,5-Iinked l -arabino-3,6-β- d -galactan structure. α-1,3-Linked l -arabinopyranose, β-1,4-linked d -xylose and α-1,4-linked d -galacturonic acid residues were also identified as the component units. The polysaccharide showed remarkable reticuloendothelial system potentiating activity in the carbon clearance test.