Isolation and identification of an anticancer compound from the bark of Acer tegmentosum Maxim

Anti-inflammatory Activity of PLA2 Inhibitory Saccharumoside-B

BACKGROUND

Saccharumoside-B and its analogs were found to have anticancer potential in vitro. The present study reports acute toxicity, molecular docking, ADMET profile analysis, and in vitro and in vivo anti-inflammatory activity of saccharumoside-B for the first time.

METHODS

The in vitro enzyme inhibitory activity of saccharumoside-B on PLA2, COX-1, COX-2, and 5-LOX enzymes was evaluated by the cell-free method, and its effect on TNF-α, IL1β, and IL- 6 secretion levels in LPS stimulated THP-1 human monocytes was determined by ELISA-based methods. The anti-inflammatory activity was evaluated in vivo by carrageenan-induced rat paw edema model. To test its binding affinity at the active site pockets of PLA2 enzymes and assess drug-like properties, docking experiments and ADMET studies were performed.

RESULTS

Saccharumoside-B showed selective inhibition of the sPLA2 enzyme (IC50 = 7.53 ± 0.232 μM), and thioetheramide-PC was used as a positive control. It showed significant inhibition (P ≤ 0.05) of TNF-α, IL-1β, and IL-6 cytokines compared to the positive control dexamethasone. Saccharumoside-B showed a dose-dependent inhibition of carrageenan-induced rat paw edema, with a maximum inhibition (76.09 ± 0.75) observed at 3 hours after the phlogistic agent injection. Saccharumoside-B potentially binds to the active site pocket of sPLA2 crystal protein (binding energy -7.6 Kcal/Mol). It complies with Lipinski's Rule of Five, showing a promising safety profile. The bioactivity scores suggested it to be a better enzyme inhibitor.

CONCLUSION

Saccharumoside-B showed significant PLA2 inhibition. It can become a potential lead molecule in synthesizing a new class of selective PLA2 inhibitors with a high safety profile in the future.

Inhibitory Effects of Compounds and Extracts from Ampelopsis brevipedunculata on IL-6-Induced STAT3 Activation

Ampelopsis brevipedunculata (Maxim.) Trautv. (AB), a traditional East Asian medicine, exhibits protective effects against several inflammatory diseases. Our search for an inhibitor of IL-6-induced JAK2/STAT3 activation revealed that AB ethanolic extract (ABE) had a significant inhibitory effect on IL-6-induced STAT3 expression in Hep3B cells. The isolation and purification of an EtOAc-soluble fraction of ABE (ABEA) using reversed-phase high-performance liquid chromatography (RP-HPLC) afforded 17 compounds. The structures of these compounds (1-17) were elucidated based on ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy as well as electrospray-ionization mass spectrometry (ESI-MS) data. ABE and ABEA were screened by a luciferase assay using Hep3B cells transfected with the STAT3 reporter gene. ABEA exhibited potent inhibitory effects on IL-6-induced STAT3 expression; moreover, these effects arose from the inhibition of the phosphorylation of the STAT3, JAK2, and ERK proteins in U266 cells. In addition, the compounds isolated from ABEA were measured for their inhibitory effects on IL-6-stimulated STAT3 expression. Of the compounds isolated, betulin showed the greatest inhibitory effects on IL-6-induced STAT3 activation in the luciferase assay (IC₅₀ value: 3.12 μM). Because of its potential for inhibiting STAT3 activation, A. brevipedunculata could be considered a source of compounds of pharmaceutical interest.

Synthesis of Saccharumoside-B analogue with potential of antiproliferative and pro-apoptotic activities

A new series of phenolic glycoside esters, saccharumoside-B and its analogs (9b-9n, 10) have been synthesized by the Koenigs-Knorr reaction. Antiproliferative activities of the compounds (9b-9n, 10) were evaluated on various cancer cell lines including, MCF-7 breast, HL-60 leukemia, MIA PaCa-2 pancreatic, DU145 prostate, HeLa cervical and CaCo-2 colon, as well as normal human MCF10A mammary epithelial and human peripheral blood mononuclear cells (PBMC) by MTT assay. Compounds (9b-9n, 10) exhibited considerable antiproliferative effects against cancer cells with IC₅₀ range of 4.43 ± 0.35 to 49.63 ± 3.59 µM, but they are less cytotoxic on normal cells (IC₅₀ > 100 µM). Among all the compounds, 9f showed substantial antiproliferative activity against MCF-7 and HL-60 cells with IC₅₀ of 6.13 ± 0.64 and 4.43 ± 0.35, respectively. Further mechanistic studies of 9f were carried out on MCF-7 and HL-60 cell lines. 9f caused arrest of cell cycle of MCF-7 and HL-60 cells at G0/G1 phase. Apoptotic population elevation, mitochondrial membrane potential loss, increase of cytosolic cytochrome c and Bax levels, decrease of Bcl-2 levels and enhanced caspases-9 and -3 activities were observed in 9f-treated MCF-7 and HL-60 cells. These results demonstrate anticancer and apoptosis-inducing potentials of 9f in MCF-7 and HL-60 cells via intrinsic pathway.

Traditional uses, phytochemistry, and pharmacology of the genus Acer (maple): A review

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Acer (Aceraceae), commonly known as maple, comprises approximately 129 species that primarily grow in the northern hemisphere, especially in the temperate regions of East Asia, eastern North America, and Europe. These plants have been traditionally used to treat a wide range of diseases in East Asia and North America. Moreover, clinical studies have shown that medicinal plants belonging to Acer are highly effective in the treatment of rheumatism, bruises, hepatic disorders, eye disease, and pain, and in detoxification. This review provides a systematic and constructive overview of the traditional uses, chemical constituents, and pharmacological activities of plants of the genus Acer.

MATERIAL AND METHODS

This review is based on a literature study of scientific journals and books from libraries and electronic sources such as SciFinder, ScienceDirect, Springer, PubMed, CNKI, Google Scholar, Baidu Scholar, and Web of Science. The literature in this review related to chemical constituents and pharmacological activities dates from 1922 to the end of October 2015. Furthermore, ethnopharmacological information on this genus was obtained from libraries and herbaria in China and USA.

RESULTS

In traditional medicine, 40 species, 11 subspecies, and one varieta of the genus Acer are known to exhibit a broad spectrum of biological activities. To date, 331 compounds have been identified from 34 species of the genus Acer, including flavonoids, tannins, phenylpropanoids, diarylheptanoids, terpenoids, benzoic acid derivatives, and several other types of compounds, such as phenylethanoid glycosides and alkaloids. Preliminary pharmacological studies have shown that the extracts and compounds isolated from this genus exhibit a broad spectrum of biological activities such as antioxidant, antitumor, anti-inflammatory, antidiabetic, hepatoprotective, and antiobesity activities, as well as promoting osteoblast differentiation. To date, reports on the toxicity of Acer species to humans are very limited, and the major safety concern of these plants is in the veterinary field.

CONCLUSIONS

Based on our systematic review, Acer species can be used to treat rheumatism, hepatic disorders, eye disease, pain, etc. effectively. Some indications from ethnomedicine have been validated by pharmacological activities, such as the anti-inflammatory and hepatoprotective activities of the species. The available literature showed that most of the activities of these species can be attributed to flavonoids and tannins. To ensure the safety and efficacy in clinical practice in the future, studies identifying active molecules and clarifying their pharmacological mechanisms as well as toxicity are needed.