[Chemistry of benzoxazinoids produced by plants as phytoalexin].

2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one and its desmethoxy derivative (DIMBOA and DIBOA) are major phytoalexins produced by rye, wheat, zea maize and related monocotyledoneae plants. These compounds elicit a wide variety of biological activities including antifungal and mutagenic activities. Structure-activity relationships of these compounds and their derivatives (benzoxazinoids), and the reactivity of benzoxazinoids with nucleophiles are discussed in relation to the molecular mechanism of their biological activity. The electrophilic reaction mechanism of benzoxazinoids and substituent effects of namely 7-methoxy and 2-hydroxy groups are also discussed.

[The effects of Arnica Montana on blood coagulation. Randomized controlled trial]. / Les effets de l'Arnica Montana sur la coagulation sanguine. Essai clinique randomisé.

The purpose of this study, which took the form of a two-period cross-over clinical trial, was to determine whether a homeopathic substance, Arnica Montana, significantly decreased bleeding time (Simplate II) and to describe its impact on various blood coagulation tests. It was not shown that this substance had a significant impact on various parameters of blood coagulation in healthy volunteers in the period immediately following administration [corrected].

Effects of Croton zehntneri aqueous extracts on some cholinergic- and dopaminergic-related behaviours of laboratory rodents.

The effects of aqueous Croton zehntneri leaf and branch extracts, orally administered, on some dopaminergic- and cholinergic-related behaviours were studied in rats and mice. The leaf extract did not modify apomorphine-induced stereotypic behavior, haloperidol-induced catalepsy and active avoidance/escape responses. The branch extract reduced stereotypy but did not interfere with catalepsy and active avoidance behavior. Both extracts were capable of increasing the tremor induced by oxotremorine.

The isolation of an active inhibitory system from an extract of aloe vera.

An Aloe vera extract was prepared with 50% ethanol. The resultant supernatant and precipitate were tested for anti-inflammatory activity using the croton oil-induced ear-swelling assay. The supernatant fraction decreased inflammation, when applied topically, by 29.2%, and the precipitate decreased inflammation by 12.1%. The authors have shown that the anti-inflammatory activity (inhibitory system) resides in the supernatant of a 50% ethanol extract.

Phytoalexins as part of induced defence reactions in plants: their elicitation, function and metabolism.

Microbial infection of plants or elicitation of cell cultures initiates substantial metabolic changes directed at the induction of defence reactions. The antimicrobial phytoalexins deserve special attention because they represent one essential component of plant resistance. The great structural diversity of phytoalexins and possible cellular sites for their toxic activity are discussed. Pterocarpan phytoalexin biosynthesis in Cicer arietinum is an example of the induction of extended biosynthetic pathways, their modes of regulation and metabolic links with constitutive secondary product formation. Elicitation of plant tissues represents a technique to induce simultaneously the formation of phytoalexins and increased levels of constitutive or other secondary products that do not normally accumulate. The biological function of phytoalexins and the pathways of their degradation by pathogenic fungi are outlined. Detoxification of phytoalexins by fungi may have important consequences for the practical application of these defence compounds and for the genetic transformation of fungi and plants. Phytoalexins accumulate in plants or cell cultures only transiently, because they are readily degraded or polymerized by extracellular peroxidases.

Isolation and effects of some ginger components of platelet aggregation and eicosanoid biosynthesis.

Aqueous ginger extract was extracted in three organic solvents viz., n-hexane, chloroform and ethyl acetate with increasing polarity. The extracted materials from these solvents reduced platelet thromboxane formation from exogenous arachidonate (AA) and also inhibited platelet aggregation induced by AA, epinephrine, ADP and collagen; in this respect they were most effective against AA-induced aggregation. The extracted material in n-hexane was further resolved by thin-layer chromatography into various fractions some of which were effective in inhibiting platelet thromboxane formation and platelet aggregation. Aqueous ginger extract reduced the formation of TxB2 from AA-labelled platelets without showing effects on platelet phospholipase activity. Thromboxane formation in labelled platelets on activation with calcium ionophore A23187 was reduced by ginger components, isolated from two TLC bands, in a dose-dependent manner (10-100 ug/500 ml). At the higher dose lipoxygenase products were also reduced. Interestingly the incorporation of AA into platelet phospholipids increased in platelets treated with aqueous ginger extract.

In vitro cytostatic activity of chromatographic fractions of extracts from some species of compositae.

Three species of the family of Compositae were extracted, partitioned and fractioned on silica gel column. The chromatographic fractions were investigated for cytostatic activity in vitro against human KB (human carcinoma of nasopharynx) cell line. The most interesting results were obtained with the first eight fractions of Senecio inaequidens DC, chloroformic extract, which showed marked cytostatic activity and appeared worthy of further investigations.

Phytoalexins.

Plants respond to infection by accumulating low-molecular-weight antimicrobial stress metabolites called phytoalexins. The phytoalexins are generally lipophilic substances that are products of a plant's secondary metabolism, and they often accumulate at infection sites to concentrations which are inhibitory to the development of fungi and bacteria. Resistance and susceptibility in plants are not determined by the presence or absence of genetic information for resistance mechanisms, including biosynthetic pathways for phytoalexin synthesis, but, rather, by the speed with which the information is expressed, the activity of the gene products, and the magnitude of the resistance response. Unlike the antibody-antigen component of the immune system in animals, low specificity is the general rule for the induction of phytoalexin accumulation and their activity against microorganisms. Annual plants can be systemically immunized against diseases caused by fungi, bacteria, and viruses by restricted infection with the pathogens, avirulent forms of pathogens, or compounds formed in immunized plants. Immunization induces plants to respond rapidly to infection with a multicomponent resistant response. The biosynthesis and accumulation of phytoalexins is one component of this resistant response. Resistance may be elicited by components in the walls and cell surfaces of fungi and bacteria and by compounds liberated from cells, their walls, or surfaces. Resistance can be enhanced or suppressed by products produced by the pathogen, the host, or by their interaction. The successful pathogen avoids recognition by the plant as nonself, suppresses the resistance response, or detoxifies its products. The actors in this play for survival on the metabolic level include the shikimate, acetate-malonate, and acetate-mevalonate pathways; glucans; oligogalacturonates; glycoproteins; lipopolysaccharides; and poly-unsaturated fatty acids. The play is directed by the genetic information of host and pathogen, and this direction is at the level of recognition and not by the presence or absence of mechanisms to contain the development of infectious agents.

Structure and function of plant cell wall polysaccharides.

Studies of the primary structures of polysaccharides of growing plant cell walls have shown that these structures are far more complex than was anticipated just a few years ago. This complexity can best be appreciated by considering xyloglucan, a hemicellulose present in the cell wall of both monocots and dicots, and rhamnogalacturonan II (RG-II) and rhamnogalacturonan I (RG-I), two structurally unrelated pectic polysaccharides. This realization led us to postulate that cell wall polysaccharides have functions beyond determining the size, shape and strength of plants. Some years ago we demonstrated that oligosaccharide fragments of a branched beta-linked glucan of fungal cell walls can elicit the production of phytoalexins (antibiotics) in plants by inducing the formation of the enzymes responsible for synthesis of the phytoalexins. It has now been ascertained and confirmed by synthesis that the elicitor activity resides in a very specific hepta-beta-D-glucoside. The heptaglucoside has been shown to elicit phytoalexins by activating the expression of specific genes, that is, by causing the synthesis of the mRNAs that encode the enzymes that synthesize phytoalexins. In other words, complex carbohydrates can be regulatory molecules. Further experiments established that oligosaccharide fragments of polysaccharides, produced by acid or base hydrolysis or by enzymolysis of primary cell walls of plants, also evoked defence responses in plants. Subsequently, we learned that defined fragments of polysaccharides, released from covalent attachment within plant cell walls, can function as regulators of various physiological processes such as morphogenesis, rate of cell growth and time of flowering and rooting, in addition to activating mechanisms for resisting potential pathogens. Examples of plant oligosaccharides with regulatory properties (called oligosaccharins) will be described.