The Importance of Flavonoids and Phytochemicals of Medicinal Plants with Antiviral Activities

: In this mini-review article, we have mentioned the key roles of some of the most important herbal plants medicines containing flavonoids and phytochemicals with antiviral activities. All relevant information was searched for terms of influenza, phytochemicals, SARS, SARS-Cov-2, flavonoids, and traditional medicinal plants uses from reliable databases, such as PubMed, Science Direct, and Google Scholar. The most important medicinal herbs which contain flavonoids with antiviral activities are Limonium densiflorum, Oroxylum indicum, Tribulus terrestris L., Paulownia tomentosa Steud., Allophylus africanus, Houttuynia cordata, Moslea Herba, Mosla scabra, Scutellaria baicalensis, Berries, Genus Psoralea, Sophora tonkinensis, Trollius chinensis, Tilia cordata, Hippophae rhamnoides L. (Seabuckthorn), Paulownia tomentosa steud, and C. swietenia. Phytochemicals are chemicals of plant origin produced by plants through primary or secondary metabolism. The most important medicinal plants which contain phytochemicals with antiviral activities are Blue honeysuckle (Lonicera caerulea L.), Forsythia suspense, Ligustrum lucidum, Radix Paeoniae Alba (Bai Shao), Banlangen (Radix Isatidis), Lysiphyllum strychnifolium, Phellinus baumii, Mesona chinensis, Sanguinaria Canadensis, Dodonaea viscosa, Isatis indigotica, Pelargonium sidoides, Entada Africana Guill., Pomegranate (Punica granatum), Goldenseal (Hydrastis canadensis), Lychee fruit extract, Lycoris radiate, Cistus incanus, Chaenomeles sinensis Koehne (Chinese quince), Geranium sanguineum L., and Tea polyphenols. Natural products from traditional herbal medicines, especially traditional Chinese and Persian medicines, have been found to exert antiviral impacts against influenza and human coronaviruses. The natural plant-derived compounds that have been used for treating various diseases are flavonoids and phytochemicals.

First report of leaf blight on Magnolia coco caused by Nothophoma quercina in China

Magnolia coco (Lour.) DC. is an ornamental shrub and widely cultivated in southern China (Nana et al. 2017). In April 2020, leaf blight symptoms were observed on the leaves of M. coco in the Chengdu campus of Sichuan Agricultural University (30°42′19.92″N, 103°51′30.61″E, 493 m) where didn’t have great protection, with roughly 70% leaves per plant were diseased. The initial symptoms presented on the leaf apex, which was manifested as dark brown spots surrounded with obvious yellowish halo (Fig. 1). As the disease progressed, spots gradually enlarged and coalesced covering the leaf, and severe infection finally caused leaf necrosis and plant decline. Four specimens from different diseased plants were used for pathogen isolation and morphological observation. Four fungal isolates were obtained from four specimens, following Chomnunti et al. (2014). Colonies on potato dextrose agar (PDA) medium were initially white and then light brown to dark brown. Pycnidia measured 284-427 × 326-554 μm (x=372.8 μm × 476.1 μm, n=20), and were brownish-black to black, broadly globose to irregular. The pycnidial wall measured 16-27 μm wide (n=20) and was composed of hyaline to brown cells of textura angularis. Conidiophores were absent, and the conidiogenous cells are pear-shaped, colorless, and smooth. Conidia measured 5-8 × 4-6 μm (x=6.5 μm × 4.6 μm, n=50), and were elliptical or subglobose, thick-walled, aseptate, hyaline, smooth, brown. These asexual structures were similar to Nothophoma quercina (Syd. & P. Syd.) Qian Chen & L. Cai described by Chen et al. (2017). The genomic DNA of representative isolate SICAUCC 21-0011 was extracted, and the internal transcribed spacers (ITS), 28S large subunit rDNA (LSU), RNA polymerase II large subunit 2 (RPB2), and beta-tubulin (TUB2) regions were amplified using the primer pairs ITS5/ITS4, LR0R/LR5, FRPB2-5F/FRPB2-7cR, and T1/BT4R, respectively. The accession numbers deposited in GenBank were MW541930 (ITS), MW541934 (LSU), MW883395 (RPB2), and MW883394 (TUB2). Nucleotide BLAST showed high homology with the sequences of N. quercina, viz. GU237900 (ITS, 485/486, 99.79%), EU754127 (LSU, 862/862, 100%), KT389657 (RPB2, 593/596, 99.49%), and GU237609 (TUB2, 333/335, 99.40%). Phylogenetic analyses based on a combined dataset showed 100% bootstrap support values in a clade with N. quercina complexes (Fig. 2). Four healthy potted plants (2-years-old) with 15 to 20 leaves per plant were sprayed with conidial suspension (105 conidia/mL) prepared from 4-week-old cultures of SICAUCC 21-0011, which incubated on PDA at 25℃, onto the wounded sites via pin-prick inoculation described by Desai et al. (2019). Another four plants were sprayed with sterilely distilled water as controls. Inoculated plants were cultured in a growth chamber (25℃, 95% relative humidity, and 12-h photoperiod). About 30 days later, brown spots were found on the inoculated leaves, which were similar to those observed in the field. There were no symptoms on the control plants, and the pathogen was re-isolated from the diseased leaves and characterized morphologically. N. quercina has been reported on Photinia × fraseri Dress, Aucuba japonica, Malus micromalus, and Chaenomeles sinensis (Mohamed et al. 2019, Lv et al. 2020, Zou et al. 2021). To our knowledge, this is the first report of leaf blight on M. coco caused by N. quercina. M. coco is one of the important ornaments in the courtyard, street, and park in China, and the risk of this pathogen needs further exploration and effective control measures should be made. Qian Zeng, Yicong Lv, and Xinyue Li contributed equally to this work.

Phenolic Constituents of Chinese Quince Twigs (Chaenomeles sinensis Koehne) and Their Anti-Neuroinflammatory, Neurotrophic, and Cytotoxic Activities

Chaenomeles sinensis has been used as a food and traditional medicines. However, most of research on discovering bioactive constituents from this plant have been focused on its yellow fruit, Chinese quince, due to its wide usage. Here, we isolated and characterized three new phenolic compounds (1, 9, and 11) and 21 known compounds (2−8, 10, and 12−24) from the twigs of C. sinensis. Their chemical structures were established by spectroscopic and spectrometric data analysis including 1D and 2D NMR, high-resolution mass spectrometry (HRMS), electronic circular dichroism (ECD), and LC-MS analysis. Some of the isolated compounds (1−24) showed anti-neuroinflammatory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 cells, neurotrophic activity in C6 cells through the secretion of nerve growth factor (NGF) and/or cytotoxicity against four human cancer cell lines (A549, SK-OV-3, SK-MEL-2, MKN-1).

First Report of leaf spot disease caused by Colletotrichum gloeosporioides on Chaenomeles sinensis in China

Chaenomeles sinensis is a shrub or small arbor of the genus Chaenomeles in Rosaceae, which is widely planted in China. It is a kind of garden ornamental plant and has high economic value. Since 2020, a leaf disease occurred on the foliage of C. sinensis at the campus of Nanjing Forestry University, Nanjing, China. After investigating, C. sinensis was found with leaf spot disease at a 100% infection rate, which causing gigantic ornamental loss. Leaf spots are round to irregular distributing on the leaves, in addition, the color of spots is brown. There are yellow halos on the edge of the lesion. Small leaf tissues (3 to 4 mm2) from lesion margins were surface sterilized with 75% ethanol for 30s and then rinsed with sterile dH2O for three times. Afterwards, placed on potato dextrose agar (PDA) at 25°C. Pure cultures were obtained by monosporic isolation, and a representative isolate (NJTJ.1) was obtained. When cultured on PDA, the colony of NJTJ.1 was white and cottony. On the reverse side, the color of colony nearly light yellow. The colony were placed in the liquid Carboxymethyl cellulose (CMC) medium. After culturing for 24h in a shaker at 25℃ and 150rmp/min, the spore liquid was taken by us. The conidia were one-celled, straight, hyaline, subcylindrical with rounded ends and measured 15.1 to 23.6× 5.4 to 7.9 µm (n =30). Appressoria were one-celled, brown, thick-walled, ellipsoidal, and measured 7.7 to 13.8 × 6.4 to 10.3 µm (n =30). The morphological characteristics of NJTJ.1 fitted with the description of the Colletotrichhum gloeosporioides complex (Weir et al., 2012). For accurate identification, the internal transcribed spacer (ITS), and the genes encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT) and chitin synthase (CHS-1) were amplified with primers ITS1/ITS4, GDF/GDR, ACT-512F/ACT-783R, and CHS-79F/CHS-345R (Zhu et al, 2019), respectively. The sequences were deposited in GenBank [Accession Nos.MT984264, MW030495 and MW030496 to MW030497 for NJTJ.1]. A Blast search of GenBank showed that ITS, GAPDH, ACT and CHS-1 sequences of NJTJ.1 were 99%, 99%, 100% and 100% identical to those of C. gloeosporioides (MH571757.1 ,KY995355.1 , MN058143.1 and MN313581.1). A neighbor-joining phylogenetic tree was generated by combining all sequenced loci in MEGA7. The isolate NJTJ.1 clustered in the C. gloeosporioides clade with 99% bootstrap support. The pathogenicity of the NJTJ.1 was verified both on detached and living leaves. The detached leaves were inoculated with 5-mm mycelial plugs cut from the edge of 6-day old cultures on PDA and 20 μL of spore suspension (106 conidia/mL) and each treatment had 5 replicates. Controls were treated with sterile dH2O. The inocula were placed at a distance of 2 to 3 cm on the leaves which were wounded with a sterile needle. All of them were placed in 20-cm dishes on wet filter paper at 25°C. After 5 days, all the inoculated points showed lesions which were similar to those outdoor observed. Whereas, controls were asymptomatic.At the same time, the plugs of C. gloeosporioides were inoculated on living leaves.After 7 days, the leaves which were inoculated also appeared lesions. This is the first report of C. gloeosporioides causing leaf blotch on Chaenomeles sinensis in China. These data will help develop effective strategies for managing this disease.

Two New Terpenoids From the Fruits of Chaenomeles sinensis (Thouin) Koehne

A new sesquiterpenoid, chaenomelesterpenoid A (1), and a new norisoprenoid, chaenomelesterpenoid B (2), were isolated from the fruits of Chaenomeles sinensis (Thouin) Koehne. Their structures were determined by NMR spectroscopy and MS. In addition, the protective effects of the compounds were tested against corticosterone-induced damage in PC-12 cells using real-time cellular analysis (RTCA). Compounds 1 and 2 significantly improved cell viability and corticosterone-induced damage in PC-12 cells with EC50 values of 15.7 and 12.6 µM, respectively.

Chemical constituents of Chaenomeles sinensis twigs and their biological activity

A new megastigmane-type norsesquiterpenoid glycoside, chaemeloside (1), was isolated from the twigs of Chaenomeles sinensis together with 11 known phytochemicals through chromatographic methods. The chemical structure of the new isolate 1 was determined by conventional 1D and 2D NMR data analysis, ECD experiment, hydrolysis followed by a modified Mosher’s method, and LC–MS analysis. The characterized compounds’ biological effects including cytotoxicity against cancer cell lines, antineuroinflammatory activity, and potential neurotrophic effect were evaluated.