Masayoshi Ohyama

Bio: Masayoshi Ohyama is an academic researcher from Gifu Pharmaceutical University. The author has contributed to research in topics: Sophora & Flavanone. The author has an hindex of 22, co-authored 32 publications receiving 1485 citations.

Flavanones with Potent Antibacterial Activity against Methicillin-resistant Staphylococcus aureus

Abstract: With the therapeutic concept of using the defensive ability of plants against microbial infections, phytoalexin, an antimicrobial phytochemical was studied for its ability to inhibit the growth of methicillin-resistant Staphylococcus aureus (MRSA) Extracts from Sophora exigua (Leguminosae) were fractionated by serial chromatography and the anti-MRSA activity of each fraction was determined by the agar-plate method Among the active isolates, 5,7,2',6'-tetrahydroxy-6-isoprenyl-8-lavandulyl-4'-methox yflavanone (exiguaflavanone D) completely inhibited the growth of all the MRSA strains examined at the concentration of 156-625 micrograms mL-1, and 5, 2',6'-trihydroxy-8-lavandulyl-7-methoxy-flavanone (exiguaflavanone B) inhibited at a concentration of 50 micrograms mL-1 This former compound is expected to be a phytotherapeutic agent for MRSA infections as an alternative to conventional antibiotics with unwanted side-effects or the appearance of antibiotic-resistant bacteria

Inhibition of the growth of cariogenic bacteria in vitro by plant flavanones.

Abstract: Phytoalexins, defensive compounds produced by plants against microbial infections, were purified from Sophora exigua (Leguminosae) and their growth inhibitory effects on oral cariogenic bacteria were determined in vitro. Among three isolated compounds, 5,7,2',4'-tetrahydroxy-8-lavandulylflavanone completely inhibited the growth of oral bacteria including primary cariogenic mutans streptococci, other oral streptococci, actinomycetes, and lactobacilli, at concentrations of 1.56 to 6.25 micrograms/ml.

Laxative effect of agarwood leaves and its mechanism.

Abstract: We investigated the laxative activity of an extract of agarwood leaves from Aquilaria sinensis. The laxative activity was measured in mice by counting the stool frequency and stool weight, and the drugs were orally administered. An acetone extract of agarwood leaves and senna (a representative laxative drug) both increased the stool frequency and weight, but a methanol extract did not. The laxative effect of the acetone extract was milder than that of the anthraquinoid laxative, senna, and the former did not induce diarrhea as a severe side effect. We identified the main constituent contributing to the laxative effect of the acetone extract as genkwanin 5-O-β-primeveroside (compound 4). Compound 4 strengthened the spontaneous motility and induced contraction in the ileum. This ileal contraction induced by compound 4 was inhibited by atropine, but not by azasetron, suggesting that the effect of compound 4 was mediated by acetylcholine receptors, and not by serotonin. The laxative mechanism for compound 4 may in part involve stimulation of intestinal motility via acetylcholine receptors.

Novel, Complex Flavonoids from Mallotus philippensis (Kamala Tree)

Abstract: One new flavanone, 4′-hydroxyisorottlerin (2), and two new chalcone derivatives, kamalachalcones C (3) and D (4), were isolated from Mallotus philippensis (kamala tree). The largest compound (4; Mr 1098 g/mol) was shown to possess a unique, fused-ring system made of two hydroxy-chalcone units, giving rise to eight fused benzene/pyran units. From the same plant, the following six known compounds were also isolated: kamalachalcone A (5) and B (6), isoallorottlerin (7), isorottlerin (8), 5,7-dihydroxy-8-methyl-6-prenylflavanone (9); 6,6-dimethylpyrano(2″,3″: 7,6)-5-hydroxy-8-methylflavanone (10), and rottlerin (1). The structures of the new compounds were confirmed by in-depth spectral analyses, including 2D-NMR techniques, and the full 13C-NMR assignments of the known flavanones 1 and 7–10 are published for the first time.

Plant Products as Antimicrobial Agents

Abstract: The use of and search for drugs and dietary supplements derived from plants have accelerated in recent years. Ethnopharmacologists, botanists, microbiologists, and natural-products chemists are combing the Earth for phytochemicals and “leads” which could be developed for treatment of infectious diseases. While 25 to 50% of current pharmaceuticals are derived from plants, none are used as antimicrobials. Traditional healers have long used plants to prevent or cure infectious conditions; Western medicine is trying to duplicate their successes. Plants are rich in a wide variety of secondary metabolites, such as tannins, terpenoids, alkaloids, and flavonoids, which have been found in vitro to have antimicrobial properties. This review attempts to summarize the current status of botanical screening efforts, as well as in vivo studies of their effectiveness and toxicity. The structure and antimicrobial properties of phytochemicals are also addressed. Since many of these compounds are currently available as unregulated botanical preparations and their use by the public is increasing rapidly, clinicians need to consider the consequences of patients self-medicating with these preparations.

Phytochemicals: nutraceuticals and human health.

Abstract: Phytochemicals, as plant components with discrete bio-activities towards animal biochemistry and metabolism are being widely examined for their ability to provide health benefits. It is important to establish the scientific rationale to defend their use in foods, as potential nutritionally active ingredients. Phytochemicals could provide health benefits as: (1) substrates for biochemical reactions; (2) cofactors of enzymatic reactions; (3) inhibitors of enzymatic reactions; (4) absorbents/sequestrants that bind to and eliminate undesirable constituents in the intestine; (5) ligands that agonize or antagonize cell surface or intracellular receptors; (6) scavengers of reactive or toxic chemicals; (7) compounds that enhance the absorption and or stability of essential nutrients; (8) selective growth factors for beneficial gastrointestinal bacteria; (9) fermentation substrates for beneficial oral, gastric or intestinal bacteria; and (10) selective inhibitors of deleterious intestinal bacteria. Such phytochemicals include terpenoids, phenolics, alkaloids and fiber. Research supporting beneficial roles for phytochemicals against cancers, coronary heart disease, diabetes, high blood pressure, inflammation, microbial, viral and parasitic infections, psychotic diseases, spasmodic conditions, ulcers, etc is based on chemical mechanisms using in vitro and cell culture systems, various disease states in animals and epidemiology of humans. However, it must be emphasized that a distinction needs to be drawn between the types of information that can be obtained from studies in vitro, in animals and in humans. Mechanisms of action must certainly be established in vitro; however, the efficacy of these same ingredients with their mechanisms of action, must also be demonstrated in vivo. The rapid growth in the use of phytochemicals in nutraceutical and functional foods requires that the food and pharmaceutical industries face new challenges: in addressing worldwide public concern over the efficacy and safety of supplements and foods claimed to be health-promoting; in government regulations related to safety, labeling and health claims for products that contain phytochemicals; in the manufacturing of foods with different qualities and stabilities; and in marketing issues, particularly as they relate to consumers' recognizing added value. © 2000 Society of Chemical Industry