New diterpenes leojaponins G–L from Leonurus japonicus

Antioxidant and anti-melanogenesis activities of extracts from Leonurus japonicus Houtt

Leonurus japonicus Houtt is an important anti-skin pigmentation herb used in traditional Chinese medicine. However, the molecular basis for this activity is complex and not fully understood. In this study, water and ethanol extracts and polysaccharide extract from L. japonicus (LJPs) were analyzed by LC-MS/MS and HPLC-DAD separately. Cytotoxicity was analyzed by using CCK-8, antioxidant activity using flow cytometer, anti-MMPs, anti-tyrosinase and signalling pathway analysis using Western blotting to investigate their anti-melanogenesis function. The results showed that the water and ethanol extracts contained alkaloids, flavonoids, and phenolic acids. The LJPs mainly contain glucose, fucose, glucuronic acid, mannose, threonine and arginine, and structure characterization by FITR analyses indicated that LJPs have β- or α-D-glycosidic bonds and contain pyranose rings. The L. japonicus extracts displayed high cell viability at their maximum concentration. The water extract and polysaccharides significantly reduced lipopolysaccharide (LPS)-induced intracellular reactive oxygen species (ROS) content and exhibited a cytoprotective role. Also, these extracts displayed higher matrix metalloproteinase-2 (anti-MMP-2), anti-MMP-9 and anti-tyrosinase activities. Furthermore, the polysaccharides displayed significantly greater inhibitory effect on intracellular ROS and tyrosinase protein expression than α-arbutin and ursolic acid used for the clinical treatment of skin pigmentation. This study also investigated the polysaccharide inhibition of melanin synthesis by repressing the expression of melanocytic lineage-specific transcription factor (MITF) and melanogenic enzymes via modulation of the phosphoinositide 3-kinase (PI3K-Akt-mTOR) and β-catenin pathways. The overall results indicate that L. japonicus is a promising candidate for anti-pigmentation treatment.

Ethnobotanical study of medicinal plants used by the Yi people in Mile, Yunnan, China

BACKGROUND

The Yi people are a sociolinguistic group living in Mile City, which is their typical settlement in southeastern Yunnan, China. Over the long history of using medicinal plants, the Yi people have accumulated and developed a wealth of traditional medicinal knowledge, which has played a vital role in their health care. However, only a few studies have been performed to systematically document the medicinal plants commonly used by the Yi people. This study provides fundamental data for the development and application of ethnomedicine as well as supports the conservation of the traditional medical knowledge of the Yi people.

METHODS

This study was conducted from May 2020 to August 2022 and involved five townships in Mile. Information regarding medicinal plants was obtained through semistructured interviews, key informant interviews, and participatory observation. The collected voucher specimens were identified using the botanical taxonomy method and deposited in the herbarium. Ethnobotanical data were analyzed using informant consensus factor, relative frequency of citation, and fidelity level.

RESULTS

In total, 114 informants distributed in five townships of Mile were interviewed. The Yi people used 267 medicinal plant species belonging to 232 genera and 104 families to treat various diseases. Asteraceae, Lamiaceae, and Fabaceae were the most commonly used plant families by the Yi people. In addition, herbs were most commonly used by the Yi people. Whole plants and roots were the preferred medicinal parts. Decoctions were the most common method of herbal medicine preparation. There are 49 different recorded diseases treated by Yi medicinal plants, and among them, respiratory diseases, rheumatism, traumatic injury, fractures, and digestive system diseases have the largest number of species used. A quantitative analysis demonstrated that plants such as Zingiber officinale, Lycopodium japonicum, Aconitum carmichaelii, Panax notoginseng, Cyathula officinalis, and Leonurus japonicus played crucial roles in disease prevention and treatment.

CONCLUSION

Traditional knowledge of medicinal plants is closely associated with the social culture of the local Yi people. The medicinal plants used for health care in the study area were diverse. Local healers were skilled at using medicinal plants to treat various diseases. Their treatment methods were convenient and unique, exhibiting distinctive regional characteristics. However, the inheritance of their traditional medicinal knowledge and protection of wild medicinal plant resources are facing serious challenges, including the decreasing number of local healers, aging of healers, lack of successors, and excessive harvesting of medicinal plant resources. This ethnobotanical survey provides a useful reference for the sustainable utilization and protection of medicinal plant resources in Mile and the inheritance of traditional medicinal knowledge of the Yi people.

Searching for Natural Plants with Antimelanogenesis and Antityrosinase Properties for Cosmeceutical or Nutricosmetics Applications: A Systematic Review

Excessive UV radiation (UVR) exposure has been shown in studies to be a major risk factor for most melanomas, causing premature skin aging as well as immune system suppression due to the increased production of hydrogen peroxide (H2O2) and other reactive oxygen species (ROS) during the melanogenesis process. Although several compounds with antioxidant and antityrosinase activities are widely used in the cosmetic industry, like kojic acid, hydroquinone, ascorbic acid, and arbutin, their use has been limited due to their adverse effects on the skin and cytotoxic issues. Recently, attempts have been made to develop new natural skin-lightening products by using plant extracts that are less toxic and exhibit numerous biological properties with great market demand. In this study, information on the depigmentation effects of various natural plant species was gathered from the SCOPUS database according to the PRISMA guidelines. A total of 414 records were retrieved, and finally, 76 articles were included in the qualitative synthesis by fulfilling all the inclusion criteria. In this review, we discuss the extraction methods and biological assays of 75 highly potential plant species, including the olive, yuzu, longan, and lotus. We concluded that the use of natural plants as skin-whitening agents is highly effective as there is a significant correlation between the content of polyphenolic compounds, antimelanogenesis, antityrosinase, and antioxidant activities. However, it is worth noting that the use of extraction methods or types of solvents is very important in determining the biological activities of plants.

Identification of four allelopathic compounds including a novel compound from Elaeocarpus floribundus Blume and determination of their allelopathic activity

Allelopathic compounds can play a vital role in protecting the environment from pollution by synthetic herbicides. Compounds isolated from plant species with allelopathic potential can be used as natural herbicides to control weeds and help reduce environmental pollution. Elaeocarpus floribundus has been reported to contain allelopathic compounds. Aqueous methanolic extracts of the leaves of this plant showed strong growth inhibitory potential against two test species (monocotyledonous Italian ryegrass and dicotyledonous alfalfa) in plants- and dose-dependent technique. Several extensive chromatographic separations of the E. floribundus leaf extracts yielded four active compounds 1, 2, 3, and 4 (novel compound). All the identified compounds showed strong growth inhibitory potential against cress. The concentrations caused for 50% growth limitation (I₅₀ values) of the cress seedlings were in the range 500.4-1913.1 μM. The findings indicate that the identified compounds might play a pivotal function in the allelopathic potential of E. floribundus tree. This report is the first on elaeocarpunone and its allelopathic potential.

Tuliposides H-J and Bioactive Components from the Bulb of Amana edulis

Three new tuliposides H-J (1-3) and 11 known compounds were obtained from the methanolic extracts of the bulbs of Amana edulis for the first time. Their structures were elucidated by NMR, MS, and IR spectroscopic data, optical rotation, and Mosher's method. The melanogenesis properties of all the isolates were evaluated in B16 melanoma cells. Consequently, tributyl citrate (9) had anti-melanogenesis activity but was cytotoxic toward B16. (+)-Pyroglutamic acid (4), (+)-butyl 5-oxopyrrolidine-2-carboxylate (6), (-)-3-hydroxy-2-methylbutyrolactone (10), and 5-(hydroxymethyl)furfural (12) had increased melanin productions and tyrosinase activities. Those active components could be further studied as the candidates against melanoma and vitiligo for skin diseases or whitening/hypopigmentation for hair.

Transdermal Delivery Systems of Natural Products Applied to Skin Therapy and Care

Natural products are favored because of their non-toxicity, low irritants, and market reacceptance. We collected examples, according to ancient wisdom, of natural products to be applied in transdermal delivery. A transdermal delivery system, including different types of agents, such as ointments, patches, and gels, has long been used for skin concerns. In recent years, many novel transdermal applications, such as nanoemulsions, liposomes, lipid nanoparticles, and microneedles, have been reported. Nanosized drug delivery systems are widely applied in natural product deliveries. Nanosized materials notably enhance bioavailability and solubility, and are reported to improve the transdermal permeation of many substances compared with conventional topical formulations. Natural products have been made into nanosized biomaterials in order to enhance the penetration effect. Before introducing the novel transdermal applications of natural products, we present traditional methods within this article. The descriptions of novel transdermal applications are classified into three parts: liposomes, emulsions, and lipid nanoparticles. Each section describes cases that are related to promising natural product transdermal use. Finally, we summarize the outcomes of various studies on novel transdermal agents applied to skin treatments.

Halimane and labdane diterpenoids from Leonurus japonicus and their anti-inflammatory activity

Ten highly oxygenated diterpenoids (nine undescribed ones) were isolated from the aerial parts of Leonurus japonicus Houtt. 14,15-Dinor-labd-5,8-dien-3,13-dione was a 14,15-dinor-labdane diterpenoid possessing a C₁₈ skeleton. 7β,9α-Dihydroxy-6-oxo-labd-13-en-15,16-amide represented a rare example of labdane diterpenoid featuring an α,β-unsaturated-γ-lactam moiety. The structures of all compounds were elucidated using spectroscopic data analyses and comparisons. The effects of these obtained compounds on nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW 264.7 cells were evaluated.(10R*,13R*,15R*)-15,16-Epoxy-6,13-dihydroxy-15-methoxy-labda-5,8-dien-7-one inhibited NO production with an IC₅₀ value of 40.1 μM.

The Guanidine Pseudoalkaloids 10-Methoxy-Leonurine and Leonurine Act as Competitive Inhibitors of Tyrosinase

Tyrosinase plays a key role in the production of melanin. A variety of industrial fields have shown interest in the development of tyrosinase inhibitors from plants. In this study, compounds 1–5 derived from Leonurus japonicas were evaluated to determine their ability to inhibit tyrosinase. Of these, 10-methoxy-leonurine (1) and leonurine (2) exhibited IC₅₀ values of 7.4 ± 0.4 and 12.4 ± 0.8 μM, respectively, and acted as competitive inhibitors of tyrosinase, with Ki values in the micromolar range. In silico modeling revealed a guanidine group located in the inner cavity and a benzene ring docked within the active site of these compounds. These guanidine pseudoalkaloids show potential not only as tyrosinase inhibitors but also as lead compounds in new scaffolds for the development of novel inhibitors.

New ent-kauran diterpene and antioxidant components from the seed of Ipomoea nil

One new ent-kauran diterpene, 7β,16β,17-trihydroxy ent-kauran 19-(6β)-olide (1), along with eight known compounds were isolated from the seed of Ipomoea nil. Isolates caffeoylquinic acid derivatives 5-9 were found for the first time in this species. All structures were identified from various spectroscopic data. trans-Caffeic acid 3, phenylpropanoid 4, and caffeoylquinic acid derivatives 5-9 could inhibit ROS generations induced in human keratinocyte HaCaT cells with IC₅₀ values of 0.94-28.40 μM. Compounds 3 and 5-9 also had DPPH free radical scavenging properties (IC₅₀ values, 14.86-68.27 μM), however, isolate 4 did not show inhibition effect. Generally, I. nil and its secondary metabolites 3-9 could be further applied for oxidative stress damage resulted in skin disorders.

Labdane-Type Diterpenoids from Leonurus japonicus and Their Plant-Growth Regulatory Activity

Thirteen new labdane-type diterpenoids 1-6, 9-11, 13, 14, 18, and 19 and seven known ones were isolated from the aerial parts of Leonurus japonicus. Compounds 1-5 represent rare examples of labdane-type diterpenoids, of which compounds 1-4 carry an N-chain linked at C-7 in their B-ring and compound 5 featured an α,β-unsaturated-γ-lactam moiety. The structures and absolute configurations of these new diterpenoids were characterized by a combination of spectroscopic techniques, X-ray crystallography, electronic circular dichroism, and calculated specific rotations. The plant-growth regulatory activity of these compounds on the growth of the roots and shoots of Lactuca sativa and Lolium perenne seedlings were evaluated. Compound 3 showed a broad-spectrum inhibitory activity with the inhibition rates ranging from 60 to 83.5% at a concentration of 200 μg/mL, which were as active as those of glyphosate. Compound 8 had a selective inhibitory activity against the growth of the roots of L. perenne seedlings with an inhibition rate of 81.7%. However, compounds 11 and 16 exhibited significant stimulation effects on the roots of L. sativa with stimulation rates of 59.8 and 65.3%, respectively. In addition, compounds 3 and 8 exhibited inhibitory effects on the germination of L. perenne seeds.