Evaluation of Microwave-Assisted Extraction Method for Preparation and Assessment of Thai Herbal Medicine Oral Tablets With Enriched Phytochemical Compounds.

In developing countries, populations have employed herbal medicines for primary health care because they are believed to be more appropriate to the human body and have less side effects than chemically synthesized drugs. The present study aimed to develop and evaluate herbal tablets incorporated with a Thai traditional medicinal extract, U-pa-ri-waat (URW), using microwave-assisted extraction (MAE). The extraction efficiency for URW using MAE and traditional solvent extraction was compared based on the percent yield after spray drying. URW tablets were prepared using the dry granulation method. The optimized products were assessed using standard characterization methods based on the United States and British Pharmacopeias. DPPH and ABTS radical scavenging assays were performed to analyze the antioxidant capacity of the microwave-assisted extracts. The results revealed that the flowability of the dry granule with added maltodextrin was improved compared to a granule without additives, as indicated by an angle of repose of 33.69 ± 2.0°, a compressibility index of 15.38 ± 0.66, and a Hausner's ratio of 1.18 ± 0.06. The resulting formulation produced flat tablets with uniform weight variation, hardness, thickness, friability, and optimum disintegration time. The URW extracts showed antioxidant activity and MAE with maltodextrin carrier displayed the strongest DPPH and ABTS radical activities with IC50 values of 1.60 ± 0.02 µg/mL and 4.02 ± 0.24 µg/mL, respectively. The URW tablet formulation passed the quality control tests. Storage of the formulation tablets for 90 days under accelerated conditions had minimal effects on tablet characteristics.

Misassigned natural products and their revised structures.

Natural products are a major pipeline for drug development and are responsible for more than 50 % of drugs on the market. NMR is a fundamental and powerful tool for the structure determination of natural products. It is essential to provide unambiguous chemical structure information on natural products in drug development research, including the structure-activity relationship, derivatization and pharmacokinetic/pharmacodynamic studies. Advancement of NMR instruments has made it possible to deal with nanomole-scale natural products for structure elucidation, but misinterpretation of NMR spectra still occurs. We review 21 natural products with revised chemical structures and the methods used for those revisions.

Creation and study of triterpenoid nanoparticles and radioprotective substance genistein.

This work is devoted to the study and obtaining of new radioprotective agents based on natural flavonoid genistein and spherical amorphous nanoparticles (SANPs) produced from a mixture of birch bark triterpenoids. The physicochemical characteristics of the nanoparticles were studied by electron microscopy, dynamic light scattering, and UV-VIS spectroscopy. The radioprotective efficacy of the nanodrug in vivo and the possibility of its use as a radioprotective agent was shown.

Single step synthesis of strigolactone analogues from cyclic keto enols, germination stimulants for seeds of parasitic weeds.

The single step synthesis of a newly designed series of strigolactones (SLs) from cyclic keto enols is described. The germinating activity of these SL analogues towards seeds of the parasitic weeds Striga and Orobanche spp. is reported. The first of these SL analogues are derived from the hydroxyl γ-pyrones kojic acid and maltol, the second type from hydroxyl α-pyrones, namely, 4-hydroxy-6-methyl-2H-pyran-2-one and 4-hydroxy-coumarin and the third type from 1,3-diketones, namely, 1,3-cyclohexane-dione (dimedone) and tricyclic 1,3-dione. All keto enols are coupled in a single step with the appropriate D-ring precursor in the presence of a base to give the desired SL analogues. All SL analogues are acceptably biologically active in inducing the germination of seeds of Striga hermonthica and Orobanchecernua. Most interesting are the analogues derived from 4-hydroxy coumarin and dimedone, as they have a remarkably high biological activity towards the seeds of parasitic weeds at relatively low concentrations, comparable with that of the general standard stimulant GR24.

Novel mitochondria-targeted antioxidants: plastoquinone conjugated with cationic plant alkaloids berberine and palmatine.

PURPOSE: To develop effective mitochondria-targeted antioxidants composed entirely of natural constituents. METHODS: Novel mitochondria-targeted antioxidants were synthesized containing plant electron carrier and antioxidant plastoquinone conjugated by nonyloxycarbonylmethyl residue with berberine or palmatine, penetrating cations of plant origin. These compounds, SkQBerb and SkQPalm, were tested in model planar phospholipid membranes and micelles, liposomes, isolated mitochondria and living cells. RESULTS: SkQBerb and SkQPalm penetrated across planar bilayer phospholipid membrane in their cationic forms and accumulated in mitochondria isolated or in living human cells in culture. Reduced forms of SkQBerb and SkQPalm as well as C10Berb and C10Palm (SkQBerb and SkQPalm analogs lacking plastoquinol moiety) revealed radical scavenging activity in lipid micelles and liposomes, while oxidized forms were inactive. In isolated mitochondria and in living cells, berberine and palmatine moieties were not reduced, so antioxidant activity of C10Berb and C10Palm was not detected. SkQBerb and SkQPalm inhibited lipid peroxidation in isolated mitochondria at nanomolar concentrations; their prooxidant effect was observed at 1,000 times higher concentrations. In human cell cuture, nanomolar SkQBerb and SkQPalm prevented fragmentation of mitochondria and apoptosis induced by exogenous hydrogen peroxide. CONCLUSION: This is the first successful attempt to construct mitochondria-targeted antioxidants composed entirely of natural components, namely plastoquinone, nonyl, acetyl and berberine or palmatine residues.

Amyrin esters induce cell death by apoptosis in HL-60 leukemia cells.

Four derivatives of an α,ß-amyrin mixture were synthesized by acylation with appropriate anhydrides. The structures of the compounds were confirmed by means of IR and (1)H and (13)C NMR. The compounds were screened for cytotoxic activity using four human tumor cell lines (HL-60, MDAMB-435, SF-295 and HCT-8) and normal peripheral blood mononuclear cells (PBMC). 3-O-Carboxymaleinate of α,ß-amyrin (3a/3b) were found to be the only active compounds of the series (high cytotoxicity), showing IC(50) values ranging from 1.8 to 3µM. In PBMC, 3a/3b were not toxic, suggesting selectivity for tumor cells. To better understand the mechanism of action involved in the cytotoxicity of 3a/3b, HL-60 cells treated with 3a/3b were examined for morphological changes, DNA fragmentation, cell cycle perturbation, externalization of phosphatidylserine and activation of caspases 3/7, with doxorubicin serving as the positive control. The results indicate that the cytotoxicity of 3a/3b involves the induction of cell death by apoptosis.

Drug discovery and development with plant-derived compounds.

An overview is given on current efforts in drug development based on plant-derived natural products. Emphasis is on projects which have advanced to clinical development. Therapeutic areas covered include cancer, viral infections including HIV, malaria, inflammatory diseases, nociception and vaccine adjuvants, metabolic disorders, and neurodegenerative diseases. Aspects which are specific to plant-based drug discovery and development are also addressed, such as supply issues in the commercial development, and the Convention on Biological Diversity.

Evaluation of natural and synthetic compounds from East Asiatic folk medicinal plants on the mediation of cancer.

In this review are presented various lead compounds bearing a polyphenolic moiety and their biological targets. The relevance of these targets to develop the desired compounds as potential anti-cancer agents is discussed. For instance, caffeic acid phenethyl ester (CAPE) has preliminary been studied in our group to hold various biochemical responses. When C6 glioma cells were grown as xenografts in nude mice, treatment with CAPE (1-10 mg/kg; ip) induced a significant dose dependent decrease in tumor growth by evaluating tumor volume and tumor weight. Histochemical and immunohistochemical analysis revealed that CAPE treatment significantly reduced the number of mitotic cells and proliferating cell nuclear antigen (PCNA)-positive cells in C6 glioma. Moreover, the ability of flavonoids to scavenge free-radicals and block lipid peroxidation raises the possibility that they may act as protective factors against carcinogenesis. Furthermore, protocatechuic acid (PCA) seems to be a promising compound regarded as a candidate group for cancer preventive agents. We have isolated and investigated Hibiscus protocatechuic acid from Hibiscus sabdariffa L. Hibiscus PCA showed against oxidative damage induced by t-butyl hydroperoxide in rat primary hepatocytes, and inhibitory effect on tumor promotion in mouse skin. Finally, we review here recent progress with the analogs of natural and synthetic lead compounds in Asiatic folk medicine. Since phenolic dimmers or trimers are significantly more potent than monomer in vitro and in vivo, a large number of phenolic dimmers or trimers with linker lengths and their pharmacological properties have been investigated.

A new class of phytoestrogens; evaluation of the estrogenic activity of deoxybenzoins.

Although deoxybenzoins are intermediates in the synthesis of isoflavones, their estrogenic activity has not been investigated. Eleven deoxybenzoins were synthesized and their estrogenicity was evaluated. While their affinities for estrogen receptors (ER) ERalpha and ERbeta were found grossly comparable to those of daidzein, some exhibited considerable selectivity and transcriptional bias toward ERbeta, which appeared to allow for enhancement of ER-mediated transcription via deoxybenzoin binding of ERbeta. Their activity to stimulate the proliferation of ER-positive breast cancer cells and regulate the expression of endogenous and stably transfected reporter genes differed considerably, with some inhibiting cell proliferation while effectively inducing gene expression at the same time. Molecular modeling confirmed that deoxybenzoins fit well in the ligand binding pocket of ERbeta, albeit with different orientations. Our data support the view that deoxybenzoins constitute a promising new class of ERbeta-biased phytoestrogens.

Constrained phytoestrogens and analogues as ERbeta selective ligands.

A new series of ERbeta (ERbeta) selective ligands has been prepared. One of the compounds 6, structurally related to the phytoestrogen apigenin 4, displays a binding preference for ERbeta over ERalpha of over 40-fold. In addition to its binding selectivity, 6 was able to potently induce metallothionein (an ERbeta specific response in human SAOS-2 cells) while demonstrating low potency in an ERalpha dependant ERE-tk luciferase assay in MCF-7 cells. Such receptor and cell selectivity could make 6 a useful molecular probe for better understanding the role of ERbeta in mammalian physiology.

Artemisinin, a novel antimalarial drug: biochemical and molecular approaches for enhanced production.

Artemisinin, a sesquiterpene lactone containing an endoperoxide bridge, has been isolated from the aerial parts of Artemisia annua L. plants. It is effective against both drug-resistant and cerebral malaria-causing strains of Plasmodium falciparum. The relatively low yield (0.01-0.8 %) of artemisinin in A. annua is a serious limitation to the commercialization of the drug. Therefore, the enhanced production of artemisinin either in cell/tissue culture or in the whole plant of A. annua is highly desirable. It can be achieved by a better understanding of the biochemical pathway leading to the synthesis of artemisinin and its regulation by both exogenous and endogenous factors. Furthermore, genetic engineering tools can be employed to overexpress gene(s) coding for enzyme(s) associated with the rate limiting step(s) of artemisinin biosynthesis or to inhibit the enzyme(s) of other pathway competing for its precursors. These aspects which may be employed to enhance the yield of artemisinin both in vitro and in vivo are discussed in this review.