José-Luis Ríos

Screening methods for natural products with antimicrobial activity: A review of the literature

Diffusion and dilution methods have been employed to study the antimicrobial activity of medicinal plants. A number of modifications have been made in the technique in order to obtain better results. Since some factors (culture medium composition, microorganisms tested, extractive method, pH, solubility of the sample in the culture medium, etc.) can change results, it is difficult using these methods to standardize a procedure for the study of antimicrobial plants. Bioautography is another method for studying antimicrobial activity. With it, previously chromatographed principles are diffused to the agar. The results can also change according to the method employed. All the various techniques are reviewed here and, in order to unify the different criteria and parameters, standard methods to study the antimicrobial activity of medicinal plants are proposed.

An Update Review of Saffron and its Active Constituents

This paper reviews the literature on recent research on the chemical composition and pharmacological activities of saffron (Crocus sativus) and its active constituents, mainly as antitumoral, hypolipidemic and tissue oxygenation enhancement agents.

Antioxidant activity of anti-inflammatory plant extracts.

The antioxidant properties of twenty medical herbs used in the traditional Mediterranean and Chinese medicine were studied. Extracts from Forsythia suspensa, Helichrysum italicum, Scrophularia auriculata, Inula viscosa, Coptis chinensis, Poria cocos and Scutellaria baicalensis had previously shown anti-inflammatory activity in different experimental models. Using free radical-generating systems H. italicum. I. viscosa and F. suspensa protected against enzymatic and non-enzymatic lipid peroxidation in model membranes and also showed scavenging property on the superoxide radical. All extracts were assayed at a concentration of 100 microg/ml. Most of the extracts were weak scavengers of the hydroxyl radical and C. chinensis and P. cocos exhibited the highest scavenging activity. Although S. baicalensis inhibited the lipid peroxidation in rat liver microsomes and red blood cells, the extract showed inhibitory actions on aminopyrine N-demethylase and xanthine oxidase activities as well as an pro-oxidant effect observed in the Fe3+-EDTA-H2O2 system. The results of the present work suggest that the anti-inflammatory activities of the same extracts could be explained, at least in part, by their antioxidant properties.

Assessment of the anti-inflammatory activity and free radical scavenger activity of tiliroside.

Three flavonoids, gnaphaliin, pinocembrin and tiliroside, isolated from Helichrysum italicum, were studied in vitro for their antioxidant and/or scavenger properties and in vivo in different models of inflammation. In vitro tests included lipid peroxidation in rat liver microsomes, superoxide radical generation in the xanthine/xanthine oxidase system and the reduction of the stable radical 1,1-diphenyl-2-pycryl-hydrazyl (DPPH). Acute inflammation was induced by application of 12-O-tetradecanoylphorbol 13-acetate (TPA) to the mouse ear or by subcutaneous injection of phospholipase A(2) or serotonin in the mouse paw. Eczema provoked on the mouse ear by repeated administration of TPA was selected as a model of chronic inflammation. The flavonoids were assayed against sheep red blood cell-induced mouse paw oedema as a model of delayed-type hypersensitivity reaction. The most active compound, both in vitro and in vivo, was tiliroside. It significantly inhibited enzymatic and non-enzymatic lipid peroxidation (IC(50)=12.6 and 28 microM, respectively). It had scavenger properties (IC(50)=21.3 microM) and very potent antioxidant activity in the DPPH test (IC(50)=6 microM). In vivo, tiliroside significantly inhibited the mouse paw oedema induced by phospholipase A(2)(ED(50)=35.6 mg/kg) and the mouse ear inflammation induced by TPA (ED(50)=357 microg/ear). Pinocembrin was the only flavonoid that exhibited anti-inflammatory activity in the sheep red blood cell-induced delayed-type hypersensitivity reaction. However, only tiliroside significantly reduced the oedema and leukocyte infiltration induced by TPA. As in the case of other flavonoids, the anti-inflammatory activity of tiliroside could be based on its antioxidant properties, although other mechanisms are probably involved.

Anti‐inflammatory and antioxidant properties of Helichrysum italicum

The anti‐inflammatory and antioxidant activities of the aerial part of Helichrysum italicum extracts have been established in various in‐vivo and in‐vitro experimental models. The results obtained on the acute oedemas induced by 12‐O‐tetradecanoylphorbol 13‐acetate (TPA) and ethyl phenylpropiolate in the mouse ear, by serotonin and phospholipase A2 (PLA2) in the mouse paw, on chronic inflammation induced by repeated application of TPA in the mouse ear and on the delayed‐type hypersensitivity induced by sheep red blood cells suggest that said anti‐inflammatory activity is due to the effects of compounds expressed via a corticoid‐like mechanism. In addition, the antioxidant activity of the extracts seems to be implicated in this anti‐inflammatory activity, as the former inhibits enzymatic and non‐enzymatic lipid peroxidation and has free‐radical scavenger properties. We conclude that the anti‐inflammatory activity of Helichrysum italicum can be explained by multiple effects, including inflammatory enzyme inhibition, free‐radical scavenging activity and corticoid‐like effects.

Chemical constituents and pharmacological properties of Poria cocos.

Poria cocos (Polyporaceae) is a saprophytic fungus that grows in diverse species of Pinus. Its sclerotium, called fu-ling or hoelen, is used in traditional Chinese and Japanese medicine for its diuretic, sedative, and tonic effects. Various studies of this fungus have demonstrated its marked anti-inflammatory activity in different experimental models of acute and chronic inflammation. It is widely used as a constituent of many preparations in Asian medicine, but the number of research papers on its clinical properties is insufficient for establishing its efficacy and safety from a scientific point of view. In this review, we have compiled all the published data concerning the chemistry, pharmacology, and clinical uses of this drug in order to evaluate its clinical interest for future use against various pathologies in which inflammation and immunodepression are implicated. We selected the papers for review on the basis of their ethnopharmacological relevance, using the most relevant databases for the biomedical sciences. Studies on various fungus extracts as well as on the major phytochemical compounds (polysaccharides and triterpenoids) present in Poria cocos comprised the principal objectives of this review. In several of the studies reviewed, the inhibitory effects of triterpenes on phospholipase A (2) (PLA (2)) have been clearly demonstrated. In addition, the inhibitory effects of Poria cocoson the secretion of different cytokines from human peripheral blood monocytes have also been described. Triterpenoids are known to have a pivotal influence on certain diseases such as rheumatoid arthritis, psoriasis, autoimmune uveitis, septic shock, and possibly bronchial asthma, while polysaccharides can potentiate the immune response. Reviewing the literature, we found that polysaccharides from Poria cocos enhanced the secretion of immune stimulators and suppressed the secretion of immune suppressors, thus potentiating the immune response. In addition, they showed antitumor activity against different cancer cell lines. This activity is associated with their capacity to inhibit angiogenesis by downregulating both NF- κB and the induction of NF- κB/Rel translocation.

Effect of selected triterpenoids on chronic dermal inflammation

The activity of four natural triterpenoids on a 12-O-tetradecanoylphorbol-13-acetate multiple-dose model of skin chronic inflammation was studied. Erythrodiol and ursolic acid were significantly effective. The most important features concerning structure-activity relationship and previous data on the effect of these triterpenoids on other inflammatory conditions are discussed.

Antimicrobial activity of selected plants employed in the Spanish mediterranean area

Eighty-one plants from the Spanish Mediterranean area employed as antimicrobial agents in folk medicine have been identified. The in vitro antimicrobial activity of chloroform and methanol extracts of the plants were studied using the agar dilution method against six selected microorganisms. Thirty extracts had activity against some of the microorganisms tested. Bioautography showed that the antimicrobial activity is probably due to flavonoids, terpenoids and phenolic acids.

Topical anti-inflammatory activity of some Asian medicinal plants used in dermatological disorders.

The topical anti-inflammatory activity of extracts from Cassia angustifolia, Rheum palmatum, Coptis chinensis, Phellodendron amurense and Scutellaria baicalensis, plants used in traditional East Asian medicine against different skin disorders, was studied. Though in different degree, all the extracts significantly inhibited the edema induced by 12-O-tetradecanoylphorbol-13-acetate (TPA), in both single or multiple application, oxazolone, and arachidonic acid (AA). None of the extracts inhibited in vitro the activity of phospholipase A(2) (PLA(2)) from Naja naja.

Influence of traditional Chinese anti-inflammatory medicinal plants on leukocyte and platelet functions.

The enzymes 5‐lipoxygenase and elastase are therapeutic targets in dermatological disorders such as psoriasis. Fifteen extracts from traditional Chinese medicinal plants used to treat topical inflammations were screened for their inhibitory effect on lipoxygenase, cyclooxygenase and elastase activity in intact leukocytes and platelets. Astragalus membranaceus, Forsythia suspensa and Poria cocos inhibited 5‐lipoxygenase, with IC50 values of 141, 80 and 141 μg mL−1, respectively. The latter two species, along with Angelica dahurica and Angelica pubescens, also inhibited elastase (IC50 values of 80, 123, 68 and 93 μg mL−1, respectively), while A. pubescens, Atractylodes macrocephala, Lentinus edodes, Rehmannia glutinosa and Paeonia lactiflora selectively inhibited 12‐(S)‐HHTrE production, a valid marker of cyclooxygenase activity. The inhibition of phospholipase A2 activity by P. cocos is discussed. Dehydrotumulosic and pachymic acids, which have been isolated from P. cocos, were shown to inhibit leukotriene B4 release. The results indicate that both P. cocos and F. suspensa are potentially valuable species in the management of skin pathologies involving chronic inflammation.