Quebrachitol: Global Status and Basic Research

Advocacy for the Medicinal Plant Artabotrys hexapetalus (Yingzhao) and Antimalarial Yingzhaosu Endoperoxides

The medicinal plant Artabotrys hexapetalus (synonyms: A.uncinatus and A. odoratissimus) is known as yingzhao in Chinese. Extracts of the plant have long been used in Asian folk medicine to treat various symptoms and diseases, including fevers, microbial infections, ulcers, hepatic disorders and other health problems. In particular, extracts from the roots and fruits of the plant are used for treating malaria. Numerous bioactive natural products have been isolated from the plant, mainly aporphine (artabonatines, artacinatine) and benzylisoquinoline (hexapetalines) alkaloids, terpenoids (artaboterpenoids), flavonoids (artabotrysides), butanolides (uncinine, artapetalins) and a small series of endoperoxides known as yingzhaosu A-to-D. These natural products confer antioxidant, anti-inflammatory and antiproliferative properties to the plant extracts. The lead compound yingzhaosu A displays marked activities against the malaria parasites Plasmodium falciparum and P. berghei. Total syntheses have been developed to access yingzhaosu compounds and analogues, such as the potent compound C14-epi-yingzhaosu A and simpler molecules with a dioxane unit. The mechanism of action of yingzhaosu A points to an iron(II)-induced degradation leading to the formation of two alkylating species, an unsaturated ketone and a cyclohexyl radical, which can then react with vital parasitic proteins. A bioreductive activation of yingzhaosu A endoperoxide can also occur with the heme iron complex. The mechanism of action of yingzhaosu endoperoxides is discussed, to promote further chemical and pharmacological studies of these neglected, but highly interesting bioactive compounds. Yingzhaosu A/C represent useful templates for designing novel antimalarial drugs.

Analyses of Antioxidative Properties of Selected Cyclitols and Their Mixtures with Flavanones and Glutathione

The conditions for determining the antioxidant properties of cyclitols (d-pinitol, l-quebrachitol, myo-, l-chiro-, and d-chiro-inositol), selected flavanones (hesperetin, naringenin, eriodictyol, and liquiritigenin) and glutathione by spectrophotometric methods—CUPRAC and with DPPH radical, and by a chromatographic method DPPH-UHPLC-UV, have been identified. Interactions of the tested compounds and their impact on the ox-red properties were investigated. The RSA (%) of the compounds tested was determined. Very low antioxidative properties of cyclitols, compared with flavanones and glutathione alone, were revealed. However, a significant increase in the determined antioxidative properties of glutathione by methyl-ether derivatives of cyclitols (d-pinitol and l-quebrachitol) was demonstrated for the first time. Thus, cyclitols seem to be a good candidate for creating drugs for the treatment of many diseases associated with reactive oxygen species (ROS) generation.

Quebrachitol inhibits biofilm formation and virulence production against methicillin-resistant Staphylococcus aureus

The present study evaluated the quebrachitol (QBC) antibiofilm and antivirulence potential against methicillin-resistant Staphylococcus aureus (MRSA). QBC inhibited MRSA biofilm formation at concentration dependent manner without affecting the bacterial growth. Then, QBC biofilm efficacy was confirmed with light and confocal laser scanning microscopy analysis. QBC treatment significantly inhibited the biofilm formation on stainless steel, titanium and silicone surfaces. Besides, QBC treatment significantly reduced the MRSA virulence productions such as lipase and hemolysis. Moreover, it reduced MRSA survival rate in the presence of hydrogen peroxide. QBC treatment inhibited the MRSA adherence on hydrophobic, hydrophilic, collagen coating and fibrinogen coating surfaces. As well as it significantly reduced the autolysin and bacterial aggregation progress. The real-time PCR analysis revealed the ability of QBC downregulated the virulence genes expression including global regulator sarA, agr and polysaccharide intracellular adhesion (PIA) encode ica. The cumulative results of the present study suggest that QBC as a potential agent to combat against MRSA pathogenesis.

Antidiabetic activities of chloroform fraction of Anthocleista vogelii Planch root bark in rats with diet- and alloxan-induced obesity-diabetes

ETHNOPHARMACOLOGICAL RELEVANCE

Anthocleista vogelii Planch is a medicinal plant traditionally used in West Africa for the management and treatment of diabetes mellitus.

AIM OF THE STUDY

To determine the antidiabetic activities of chloroform fraction (CF) of Anthocleista vogelii Planch root bark in rats with diet- and alloxan-induced obesity-diabetes.

MATERIALS AND METHODS

Inhibitory activities of CF against α-amylase and α-glucosidase activities were determined in vitro. Three weeks old rats were fed with high-fat diet for 9 weeks to induce obesity prior to further induction of diabetes using alloxan (150 mg/kg body weight, i.p.). Blood glucose levels and body weight were measured every 7 days throughout the experiment. Glucose tolerance was assessed in normal and CF-treated rats on day 21. Terminal blood samples were collected from sacrificed animals for the measurement of serum insulin levels. Pancreases were excised from treated and untreated animals for histopathological examination.

RESULTS

LCMS/MS chromatographic profile of CF via positive and negative modes revealed 13 and 23 compounds respectively. Further analysis revealed quebrachitol (QCT), loganin, sweroside, oleoside 11-methyl ester and ferulic acid, which have been previously reported for their antidiabetic activities, as constituents of CF. CF inhibited activities of α-amylase (IC₅₀ = 51.60 ± 0.92 µg/ml) and α-glucosidase (IC₅₀ = 5.86 ± 0.97 µg/ml) in a dose-dependent manner. Treatment of animals with obesity-diabetes with 100 and 200 mg/kg CF significantly improved glucose tolerance (P < 0.001) and enhanced serum insulin levels (P < 0.05) compared to diabetic control rats.

CONCLUSIONS

Antidiabetic activities of CF might be mediated via inhibition of α-amylase and α-glucosidase activities, elevation of serum insulin concentration, and enhancement of insulin and leptin sensitivity in obesity-diabetes rats. This study further substantiates the traditional use of A. vogelii in the management and treatment of diabetes in Africa and encourages further studies to investigate its mechanism of action.

l-Quebrachitol Promotes the Proliferation, Differentiation, and Mineralization of MC3T3-E1 Cells: Involvement of the BMP-2/Runx2/MAPK/Wnt/β-Catenin Signaling Pathway

Osteoporosis is widely recognized as a major health problem caused by an inappropriate rate of bone resorption compared to bone formation. Previously we showed that d-pinitol inhibits osteoclastogenesis but has no effect on osteoblastogenesis. However, the effect on osteoblast differentiation of its isomer, l-quebrachitol, has not yet been reported. The purpose of this study was, therefore, to investigate whether l-quebrachitol promotes the osteoblastogenesis of pre-osteoblastic MC3T3-E1 cells. Moreover, the molecular mechanism of action of l-quebrachitol was further explored. Here, it is shown for the first time that l-quebrachitol significantly promotes proliferation and cell DNA synthesis. It also enhances mineralization accompanied by increases in mRNA expression of bone matrix proteins including alkaline phosphatase (ALP), collagen type I (ColI), osteocalcin (OCN), and osteopontin (OPN). In addition, l-quebrachitol upregulates the mRNA and protein expression of bone morphogenetic protein-2 (BMP-2) and runt-related transcription factor-2 (Runx2), while down-regulating the receptor activator of the nuclear factor-κB ligand (RANKL) mRNA level. Moreover, the expression of regulatory genes associated with the mitogen-activated protein kinase (MAPK) and wingless-type MMTV integration site (Wnt)/β-catenin signaling pathways are also upregulated. These findings indicate that l-quebrachitol may promote osteoblastogenesis by triggering the BMP-2-response as well as the Runx2, MAPK, and Wnt/β-catenin signaling pathway.