John L. Etchells

Pectinase and Cellulase Enzyme Inhibitor from Sericea and Certain Other Plants

A water-soluble substance isolated from the leaves of seven plant species is shown to inhibit the fungal hydrolytic enzymes, pectinase and cellulase. Three plants-sericea, muscadine grape, and persimmon-were found to be good sources of the inhibitor. Preparations of all three, isolated by the caffeine-complex method, were rated about equal in enzyme inhibition, and their chemical and physical characteristics were found to be essentially the same. When sericea was harvested in the field with a silage cutter, inhibitor activity was rapidly lost as compared to harvesting by cutting the whole stalk. Total tannin content did not appreciably change under any of the conditions of harvesting or dehydration. Grape-leaf and sericea-enzyme inhibitor are both of high molecular weight (14,000-20,000) and have certain chemical reactions that place them as condensed polymers of catechins or leucoanthocyanidins.

PECTINASE INHIBITOR IN GRAPE LEAVES

1. A water-soluble substance in grape leaves which inhibits both purified polygalacturonase (PG) and pectinase from mold-laden cucumber flowers is reported. 2. Of the six grape varieties tested, the leaves from the Scuppernong variety of the Muscadine group (Vitus rotundifolia Michx.) contained the highest inhibitor content. 3. The inhibiting substance was stable to heat, non-dialyzable through cellophane membrane against running tap water and distilled water, and could not be completely precipitated with acetone or concentrated ammonium sulfate. 4. The reduction in pectinase activity obtained was directly related to the inhibitor concentration used. The reaction between polygalacturonase, the substrate, and the inhibitor (acetone-powder preparation) was that of competitive inhibition.

Inhibition of Pectinase and Cellulase by Certain Plants

1. The water-soluble leaf extracts from 61 plant species in 32 families were screened for their ability to inhibit two hydrolytic fungal enzymes, cellulase and pectinase. 2. Leaf extracts from 29 species inhibited pectinase and extracts from 14 inhibited cellulase. 3. The leaves from muscadine grape, persimmon, dogwood, blueberry, sericea, blackberry, raspberry, and rose were considered good sources for the pectinase inhibitor as measured against cucumber-flower pectinase and a commercial pectinase. 4. In general, cellulase inhibition by the different plant species was less pronounced than that observed for pectinase. The first five species listed in the previous paragraph gave strong inhibition of cucumber-flower cellulase. Muscadine grape and persimmon were the only two species which inhibited the commercial cellulase enzyme 19AP, and then only moderate to weak inhibition was obtained.

Cellulase Inhibitor in Grape Leaves

1. A water-soluble substance in grape leaves which inhibits the enzymatic hydrolysis of soluble cellulose is reported. The mature leaves of six grape varieties of the Muscadine group (Vitis rotundifolia Michx.) were found to be good sources of the inhibitor. 2. The reduction in cellulase activity obtained was directly related to the concentration of inhibitor used. Cucumber-flower cellulase was more sensitive to inhibition by the grape-leaf substance than were the four commercial cellulases studied. 3. The grape-leaf extracts containing the inhibiting substance were stable to heat, to weak acid and alkali, and to such protein precipitating agents as trichloroacetic acid. The inhibitor was non-dialyzable through cellophane or collodion membranes against water or weakly buffered solutions (3 days). 4. The cellulase-inhibiting substance is not related in structure to carbohydrates or proteins and appears to be a high-molecular-weight organic constituent.

Nutritive Value of Brined and Fermented Vegetables

THE urgency of the food production and preservation program which has faced this nation for the past year cannot be overemphasized. This critical food problem still remains unsolved. To assist in meeting the challenge presented, research men and commercial food processors alike are investigating the possibilities offered by all methods of food preservation. The salting or brining of food is one of the oldest preservation methods practised by man. Today we recognize that this method still offers tremendous possibilities both for commercial and home preservation of many foods. An adequate study. of the nutritive value of foods preserved by any method should properly include a comparison of the nutritive quality of the processed foods with that of the fresh produce before processing. Generally speaking, a loss in nutrients takes place whenever food is processed whether such treatment be for the purpose of preservation or for cooking for table use. Such loss is dependent upon the products receiving treatment, the processing treatments given, and the care exercised during processing. The nutrient constituents of a food