Chalcone synthase catalyzes the initial step of that branch of the phenylpropanoid pathway that leads to flavonoids. A lack of chalcone synthase activity has a pleiotropic effect in maize and petunia mutants: pollen fertility as well as flavonoid synthesis is disrupted. Both maize and petunia mutants are self-sterile due to a failure to produce a functional pollen tube. The finding that the mutant pollen is partially functional on wild-type stigmas led to the isolation and identification of kaempferol as a pollen germination-inducing constituent in wild-ype petunia stigma extracts. We show that adding micromolar quantities of kaempferol to the germination medium or to the stigma at pollination is sufficient to restore normal pollen germination and tube growth in vitro and full seed set in vivo. Further we show that the rescue ability resides in particular structural features of a single class of compounds, the flavonol aglycones. This rmding identifies another constituent of plant reproduction and suggests that addition or removal of the flavonol signal during pollen germination and tube growth provides a feasible way to control plant fertility.

Wine model systems containing equlmolar quantities of malvidindglucoside and d-catechin, with and without acetaldehyde, were stored anaerobically at 22, 32, 42, and 52°C. Malvidind-glucoside and d-catechin disappearance and polymer appearance were monitored by HPLC and calorimetric methods. Reaction rates and activation energies were calculated. The malvidin3glucoside and d-catechin condensation reactions showed pseudo fist order kinetics both with and without the presence of acetaldehyde. However, activation energies were not significantly different.

The antifungal activities of caffeic, p‐coumaric, ferulic, and chloro‐genie acids against Saccharomyces cerevisiae were investigated. Caffeic acid was found to exhibit little inhibition of growth, although the lag period was extended in the presence of 1000 ppm. Chloro‐genie acid had no effect on the organism. In contrast, p‐coumaric acid at 100 ppm increased the lag phase of S. cerevisiae, and above 250 ppm, inhibition after 72 hr growth was proportional to the concentration present. Ferulic acid caused an increase in lag phase at 50 ppm, while as little as 250 ppm resulted in complete inhibition. These results suggest that naturally occurring hydroxycinnamates may interfere with the fermentation of fruits by this yeast.

SUMMARY— Growth rate studies were conducted with Pseudomonas aeruginosa to measure the inhibitory effect of CO2 when such variables as temperature, O2, tension, pH, and ionic strength of the glucose‐salts medium were controlled. Depletion of O2 did not limit growth until more than 75% (v/v) of the air was replaced with nitrogen. Generation time increased with ionic strength of the medium. The influence of pH in the range of 6.0 to 7.4 on the growth rate was negligible. When these variables were controlled, a linear relationship between generation time and CO2 composition of the gas phase was observed. At 70% CO2 (v/v), the generation time was nearly doubled. Thus, CO2 inhibits the metabolism of the organism, and this inhibition is due to gaseous CO2 in the air only when other environmental factors are controlled.

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Malvidin 3,5-diglucoside and (+)-catechin react in aqueous 10 mM HC1 to form a colorless, C4, bicyclic condensation product. Chromatographic, chemical, and NMR data support assignment of structure IV for this condensation product. The relevance of this condensation reaction to the phenolic polymerizations that occur in red wines during aging is discussed.During the aging of red wines anthocyanin pigments undergo condensation reactions producing polymeric pigments. These polymers are responsible for the characteristic spectral changes observed in aged wines and are associated with reduced astringency (Singleton and Noble, 1976). Two main reaction pathways are considered to account for the formation of these polymeric pigments: (1) a direct condensation between the electrophilic pyrilium ring of anthocyanins and the aromatic ring of other phenolics such as catechin; (2) a Baeyer condensation involving addition of acetaldehyde to a flavanol followed by electrophilic substitution of this intermediate onto another flavanol or anthocyanin (Jurd, 1967). In the latter the resonance of the anthocyanin would not be directly affected by substitution. A complex alternating sequence of anthocyanin and flavanol could result in a highly pigmented polymer having spectral properties similar to those of monomeric anthocyanins. The direct condensation mechanism is complex but presumably must involve the formation of colorleas flavenyl-flavanol intermediates that then are oxidized to xanthylium or pyrillium salts (Jurd, 1967(Jurd, , 1972Jurd and Somers, 1970).Timberlake and Bridle (1976) have studied these reactions in model systems and have presented evidence for the formation of acetaldehyde-bridged intermediates and xanthylium salts. They did not isolate a direct condensation dimer (a flavenyl glycoside-flavanol). A more complete understanding of the properties of acetaldehyde-bridged and direct-condensed polymers might make it possible to define the relative importance of these reactions in aging of red wines. The production and characterization of a bicyclic malvidin 3,5-diglucosidecatechin condensation product are reported in this paper. MATERIALS AND METHODSThe equipment used for HPLC consisted of two Waters Associates (Milford, MA) Model 6000 A pumps and aModel 660 solvent programmer. The detector was a Perkin-Elmer (Norwalk, CT) LC 75 variable-wavelength detector. Peak areas and retention times were measured with a Spectra-Physics minigrator (Santa Clara, CA). Both the analytical and preparative columns were packed with reversed-phase (C1& silica. The preparative column (9.4 mm i.d. X 25 cm) has been previously described (Wulf and Nagel, 1978). The 4.6 mm i.d. X 25 cm analytical column was purchased from Supelco, Inc. (Bellefonte, PA). The following conditions were used for HPLC separation of the 99164-6330. 99164-4660. compounds unless otherwise stated: Solvent A, 0.01 M trifluoroacetic acid (TFA) in water; solvent B, 0.01 M TFA and 40% (v/v) acetonitrile in water; flow rate, 2.0 mL/min; initial conditions, 34% solvent B f...

Thermal stability of lipoxygenase (LOX) and peroxidase (POD) in fresh asparagus tips and partially purified asparagus LOX and POD were compared. In all cases, heating at 50, 60 and 70°C resulted in higher percentages of residual LOX activity than POD activity. Inactivation of LOX followed first order kinetics while inactivation of POD followed a biphasic curve. Activation energies for thermal denaturation of the partially purified enzymes were 47.5 kcal/mol for LOX and 41.9 kcal/mol for POD.

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