Chemical constituents of the stem bark of Morus cathayana

Structures, activities, and putative biosynthetic pathways of characteristic polyphenolic compounds from Morus plants: A review

Morus plants played a pivotal role in ancient Chinese sericulture and silk production, which served as critical components of economy and culture. Besides, many parts of mulberry trees, including roots, leaves, stems, and fruits, hold various medicinal value, and have been utilized in traditional medicine for thousands of years. The chemical composition of mulberry has been reported in many literatures, while the characteristic compounds have not been systematically summarized. In this review, we focused on the polyphenolic compounds in mulberry, including flavonoids, 2-arylbenzofurans, and Diels-Alder (D-A) adducts, and summarized their structural features, structure-activity relationships, and potential biosynthetic pathways. The results revealed a characteristic class of 2'-hydroxylated flavonoids and stilbenes which played an important role in the biosynthesis of downstream 2-arylbenzofurans and D-A adducts in mulberry but had been overlooked by most studies. The prenylated modifications of different compounds were also discussed and their function as precursors of D-A adducts was emphasized. We also describe the effects of different modifications on biological activities. Besides, the chemical composition of Morus was most similar to that of Artocarpus in the Moraceae family in that they had almost identical characteristic compounds. Finally, a putative total biosynthetic pathway of D-A adducts in mulberry was proposed based on structure derivation and combination of verified reactions. This review contributes to the understanding of the biological activity and biosynthesis of the characteristic components of Morus plants.

Competitive CatSper Activators of Progesterone from Rhynchosia volubilis

The root Rhynchosia volubilis was widely used for contraception in folk medicine, although its molecular mechanism on antifertility has not yet been revealed. In human sperm, it was reported that the cation channel of sperm, an indispensable cation channel for the fertilization process, could be regulated by various steroid-like compounds in plants. Interestingly, these nonphysiological ligands would also disturb the activation of the cation channel of sperm induced by progesterone. Therefore, this study aimed to explore whether the compounds in R. volubilis affect the physiological regulation of the cation channel of sperm. The bioguided isolation of the whole herb of R. volubilis has resulted in the novel discovery of five new prenylated isoflavonoids, rhynchones A - E (1:  - 5: ), a new natural product, 5'-O-methylphaseolinisoflavan (6: ) (¹H and ¹³C NMR data, Supporting Information), together with twelve known compounds (7:  - 18: ). Their structures were established by extensive spectroscopic analyses and drawing a comparison with literature data, while their absolute configurations were determined by electronic circular dichroism calculations. The experiments of intracellular Ca²⁺ signals and patch clamping recordings showed that rhynchone A (1: ) significantly reduced cation channel of sperm activation by competing with progesterone. In conclusion, our findings indicat that rhynchone A might act as a contraceptive compound by impairing the activation of the cation channel of sperm and thus prevent fertilization.

Microbial Transformation and Biological Activities of the Prenylated Aromatic Compounds from Broussonetia kazinoki

Broussonetia kazinoki has been used as a traditional medicine for the treatment of burns and acne, and its extracts have been found to show tyrosinase inhibitory and anticancer activities. In this study, the tyrosinase inhibitory and cytotoxic activities of B. kazinoki were explored, leading to the isolation of kazinol C (1), kazinol E (2), kazinol F (3), broussonol N (4), and kazinol X (5), of which the compounds 4 and 5 have not been previously reported. Microbial transformation has been recognized as an efficient tool to generate more active metabolites. Microbial transformation of the major compounds 1 and 3 was conducted with Mucor hiemalis, where four glucosylated metabolites (6-9) were produced from 1, while one hydroxylated (10) and one glucosylated (11) metabolites were obtained from 3. Structures of the isolated metabolites were determined by extensive spectroscopic analyses. All compounds were evaluated for their tyrosinase inhibitory and cytotoxic activities. Compound 3 and its metabolites, kazinol Y (10) and kazinol F-4″-O-β-d-glucopyranoside (11), exhibited the most potent tyrosinase inhibitory activities with the IC₅₀ values ranging from 0.71 to 3.36 µM. Meanwhile, none of the metabolites, except for kazinol C-2',3″-di-O-β-d-glucopyranoside (7), showed moderate cytotoxic activities (IC₅₀ 17.80 to 24.22 µM) against A375P, B16F10 and B16F1 cell lines.

Bioactive Isolates of Morus Species as Antibacterial Agents and their In Silico Profiling

Background:

The genus Morus is one of the rich sources of phytomedicine and considered a beneficial natural source for drugs with potential antimicrobial effect under the traditional system of medicine.

Introduction:

In the present study, three bioactive compounds isolated from the leaves of two species of genus Morus and their antibacterial effect against selective pathogens were assessed.

Methods:

The inhibitory effects of the three molecules isolated were assessed for their minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) against selected pathogens. The in-silico studies provided the toxicity profile and the binding interactions with glucosamine- 6-phosphate synthase for all the isolates.

Results:

Among the three compounds tested, cathafuran-B showed a prominent bacteriostatic and bactericidal effect, which is supported by the results of in-silico analysis suggesting that cathafuran- B could be a potential glucosamine-6-phosphate synthase inhibitor.

Conclusion:

The biomolecule isolated from less explored Morus laevigata exhibiting higher antibacterial effect among the compounds tested warranted opening a new prospect in phytomedicinal research for exploring its pharmacological properties and lowering the utilization load present on highly explored Morus alba.

The structure-activity relationship review of the main bioactive constituents of Morus genus plants

Abstract

Morus genus plants are mainly distributed in the temperate to tropical areas over the world and include 17 species and two subspecies. Due to their excellent pharmacological activity, security in food additives and high value in the national economy, Morus genus plants have drawn more and more attention in recent years. In the light of the references published over the last few decades, flavonoids, benzofurans, stilbenes, and Diels–Alder adducts have been reported to be the main bioactive constituents of Morus genus plants. This review summarizes the compounds with excellent bioactivities isolated from Morus genus plants as well as their structure–activity relationships (SARs), which might be useful for the further research and development of Morus genus plants.

Graphic abstract

The aromatic heterocycles with excellent bioactivities isolated from Morus genus plants as well as their structure–activity relationships (SARs) were summarized.

Bioactive Benzofuran Derivatives from Cortex Mori Radicis, and Their Neuroprotective and Analgesic Activities Mediated by mGluR₁

Four new benzofuran-type stilbene glycosides and 14 known compounds including 8 benzofuran-type stilbenes and 6 flavonoids were isolated from the traditional Chinese medicine, Cortex Mori Radicis. The new compounds were identified as (9R)-moracin P 3′-O-α-l-arabinopyranoside (1), (9R)-moracin P 9-O-β-d-glucopyranoside (2), (9R)-moracin P 3′-O-β-d-glucopyranoside (3), and (9R)-moracin O 10-O-β-d-glucopyranoside (4) based on the spectroscopic interpretation and chemical analysis. Three benzofuran-type stilbenes, moracin O (5), R (7), and P (8) showed significant neuroprotective activity against glutamate-induced cell death in SK-N-SH cells. In addition, moracin O (5) and P (8) also demonstrated a remarkable inhibition of the acetic acid-induced pain. The molecular docking with metabotropic glutamate receptor 1 (mGluR₁) results indicated that these neuroprotective benzofuran-type stilbenes might be the active analgesic components of the genus Morus, and acted by mediating the mGluR₁ pathway.

Two new flavonoids from Morus notabilis

Phytochemical investigation of the twigs of Morus notabilis led to the isolation and characterization of two new flavonoids, notabilisin F (1) and notabilisin G (2). Their structures were elucidated on the basis of extensive spectroscopic analysis.

The latest review on the polyphenols and their bioactivities of Chinese Morus plants

The mulberry tree (Morus alba) plays a key role in agriculture, and its different parts have been used as popular Traditional Chinese Medicines for thousands of years. There are 16 species belonging to the Morus genus. Among them, 11 species distribute in China, most of which have been used as the substitutes of M. alba in local provinces. This review summarizes the structural characters of polyphenols, the main components in Morus, including Diels-Alder-type adducts, flavonoids, 2-arylbenzofurans, and stilbenes, and also their related bioactivities in the last 10 years.

Analysis of Functional Constituents in Mulberry (Morus alba L.) Twigs by Different Cultivars, Producing Areas, and Heat Processings

Four functional constituents, oxyresveratrol 3'-O-β-D-glucoside (ORTG), oxyresveratrol (ORT), t-resveratrol (RT), and moracin (MC) were isolated from the ethanolic extract of mulberry (Morus alba L.) twigs by a series of isolation procedures, including solvent fractionation, and silica-gel, ODS-A, and Sephadex LH-20 column chromatographies. Their chemical structures were identified by NMR and FABMS spectral analysis. Quantitative changes of four phytochemicals in mulberry twigs were determined by HPLC according to cultivar, producing area, and heat processing. ORTG was a major abundant compound in the mulberry twigs, and its levels ranged from 23.7 to 105.5 mg% in six different mulberry cultivars. Three other compounds were present in trace amounts (<1 mg/100 g) or were not detected. Among mulberry cultivars examined, "Yongcheon" showed the highest level of ORTG, whereas "Somok" had the least ORTG content. Levels of four phytochemicals in the mulberry twigs harvested in early September were higher than those harvested in early July. Levels of ORTG and ORT in the "Cheongil" mulberry twigs produced in the Uljin area were higher than those produced in other areas. Generally, levels of ORTG and ORT in mulberry twigs decreased with heat processing, such as steaming, and microwaving except roasting, whereas those of RT and MC did not considerably vary according to heat processing. These results suggest that the roasted mulberry twigs may be useful as potential sources of functional ingredients and foods.

The advent of genomics in mulberry and perspectives for productivity enhancement

Sericulture in India is a highly remunerative industry, especially for the rural population. Mulberry is an extremely versatile plant, having multifaceted applications, the most important being the sole feed for the monophagus silkworm, Bombyx mori. Profitability of the sericulture industry is directly correlated with production of high-quality mulberry leaves. However, mulberry productivity is severely impacted by abiotic as well as biotic stresses. Therefore, to develop stress-tolerant mulberry with desired characteristics, a comprehensive understanding and utility of biotechnological resources is essential. Research efforts on mulberry encompass broad range of fields in plant biology from breeding, molecular markers, transcriptomics, proteomics, and metabolomics. Additionally, a large number of mulberry germplasm accessions have been maintained and evaluated in several countries. Identification of superior cultivars under stressed regimes is extremely important, and therefore, physiological traits have often been used as proxy genetic markers for assessing stress tolerance index. Mulberry genomic resources have provided a limited but an important list of novel candidate genes, thus enhancing the scope for future investigations for improvement of its productivity. The present review article gives a bird's eye view of current initiatives of genomics advancements in mulberry research and enumerates the prospects for enhancing its productivity.