Polyphenol oxidases and peroxidases are among the most studied enzymes in fruits and vegetables. Owing to the deleterious effects of discoloration and off-flavor formation induced by their actions, these enzymes have not ceased to be a matter of concern to food technologists, while their versatility as catalyst and their diversity as protein present a challenge to the biochemist. This article gives an account on the present state of knowledge in this field. The occurrence of polyphenol oxidases and peroxidases in food and food raw materials, and their role and importance in food processing are briefly outlined. Results of biochemical research including catalytic properties, substrate specificity, susceptibility towards pH and temperature, action of inhibitors, isolation, purification, and characteristics of the enzymes are given, with special emphasis on recent achievements based on high resolution separation and isoenzyme techniques. Finally, the behavior of polyphenol oxidase and peroxidase in selected major groups of fruits and vegetables is discussed. Some contradictions found in the literature are pointed out and some questions that have not been given the necessary attention by researchers so far are mentioned.

Polyphenol oxidase and peroxidase in fruits and vegetables.

The proximate composition, amino acid profile and functional properties of isolated winged bean proteins were determined and compared with soy protein isolate. Winged bean protein extracted at pH 10 and pH 12 had protein contents of about 90% and 80%, respectively. Alkali extraction of winged bean proteins at pH 10 and pH 12 did not affect the amino acid distribution of the isolated proteins. Oil and water absorption, emulsion, and foaming properties of winged bean isolated compared favorably with soy isolate. Least gelation concentration for winged bean isolate was 18% compared to 14% for soy isolate. Thus, winged bean protein isolate with its high protein content, high lysine and other essential amino acid content and good functionality has a good potential as an ingredient in food products.

Physicochemical and Functional Properties of Winged Bean Flour and Isolate Compared with Soy Isolate

Undoubtedly medicinal plants are relevant in both developing and developed nations of the world as sources of drugs or herbal extracts for various chemotherapeutic purposes Also the use of plantderived natural compounds as part of herbal preparations as alternative sources of medicaments continues to play major roles in the general wellness of people all over the world The African continent contains some of the richest biodiversity in the world, and abounds in plants of economic importance and plants of medicinal importance which when developed would reduce our expenditure on imported drugs to meet our health needs Herbal-based and plant-derived products can be exploited with sustainable comparative and competitive advantage This review presents some indigenous African plants with chemotherapeutic properties and possible ways of developing them into potent pharmacological agents using biotechnological approaches

https://www.ajol.info/index.php/ajb/article/view/14899/58643

African indigenous plants with chemotherapeutic potentials and biotechnological approach to the production of bioactive prophylactic agents

Pollination is a process that is vital for the survival not only of flowering plants, but also for mankind. Yet human efforts to manipulate the reproduction of crop plants have been largely empirical. Today, research into plant reproduction is not given high priority. Yet it provides the means of ensuring successful pollination, in order to maximize fertilization and hence crop production. The pollination process is susceptible to modification to permit the introduction of desirable genes, for example, for disease resistance, from wild species into crop plants. The potential applications are endless, yet all depend on a precise knowledge of the events of pollination (see reviews by STanley and LInskens 1974, FRankel and GAlun 1977, CLarke and KNox 1978).

Pollen-Pistil Interactions

Pigments in Vegetables

Nutritional composition of okra seed meal

Immature okra pods are commonly consumed as a vegetable. In addition, okra has attributes that could permit it to be used for other purposes. Leaves, buds, and flowers are edible; dried seeds could provide oil, protein, vegetable curd and a coffee additive or substitute. Foliage could be used for biomass, and the dried stems could serve as a source of paper pulp or fuel. The possible gossypol and cyclopropenoid contents of okraseed must be considered when food or feed use for monogastrates is contemplated. Although little development work has been done with okra, available germ plasm appears to be sufficiently diverse to permit genetic improvement.

Okra, potential multiple-purpose crop for the temperate zones and tropics

Chromosomes were counted at meiosis and mitosis in 4 sapogenin-bearing species of Dioscorea and 9 other species. Chromosome numbers of 7 New-World species are reported herein for the first time. In these, 2n numbers were 36 except in two lines of D. floribunda which contained 54-chromosomes and showed irregular meiosis. All New-World species counted had chromosome numbers which are multiples of 9, whereas all Old-World species had numbers which are multiples of 10. The significance of the findings is discussed with reference to origin and distribution of the genus, processes of speciation, and possible barriers to breeding.

Chromosome Numbers and Behavior in Some Species of Dioscorea

Species of the Convolvulaceae were screened for both self- and cross-incompatibility reactions. Self-fertile species (38 found) were mostly weedy or ornamental annuals. Self-incompatible species (13 found) were large-flowered perennials (one exception) with extrorse dehiscence of anthers. Both self- and inter-specific incompatibilities were caused chiefly by failure of pollen to germinate. In addition, pollen tubes frequently failed to pass from stigma to style. This latter phenomenon was associated chiefly with crosses between partially sterile species. From a physiological standpoint, self-incompatibility thus resembles, and may have evolved from, a generally occurring system of interspecific incompatibility.

Self- and Interspecific Incompatibility in the Convolvulaceae

A B S T R A C T Extracts of the intact stigmatic surface of 10 species from different families contained little or no free sugar. The principal components of the extracts consisted of phenolic (anthocyanins, flavonoids, cinnamic acids) and lipid compounds. The phenolic compounds occurred as glycosides or esters. Phenolic compounds could inhibit insects and diseases, stimulate or inhibit pollen germination, or provide specificity to the pollen selection-germination process of the stigma by interacting with growth-regulators or related compounds. THE EXUDATE of the stigma, sometimes called the stigmatic fluid, has been assumed to be an aqueous solution of sugars that plays a role in the pollen-germination process. Because of this assumption, media to germinate pollen in vitro are invariably aqueous in nature (Brewbaker and Kwack, 1963; Linskens, 1964). Studies of the respiration of pollen during germination have been made in aqueous media (Dickinson, 1967). Blocks of agar, gelatin, and sucrose in water have been applied to the stigma to provide a germinating medium and to overcome incompatibility barriers (Swaminathan, 1955). Calcium to stimulate pollen germination was applied in an aqueous solution (Kwack, 1965). In only a few cases has the stigmatic secretion been subject to investigation. Moewus (1950) suggested that the physiological controls of heterostylic self-incompatibility of Forsythia was associated with the presence of certain flavone glycosides on the stigma. Each alternative form of the species lacked the enzyme necessary to hydrolyze the compounds produced on its own style, but contained the enzyme necessary to hydrolyze compounds of the stigma of the opposite form. Baum (1950) characterized as a "resin" the thick greasy exudate of the stigmas of Koelreuteria paniculata Laxmann. The material was soluble in acetic acid but not in water, alcohol, or ether. Vasil and Johri (1964) found lipid compounds in the stigmatic secretions of Aegle marmelos Corr. and Pavonia zeylanica Cav. Konar and Linskens (1966) suggested that the oily exudate (chiefly esters of fatty acids) of the stigma of Petunia controlled the osmotic relations of the germinating pollen. This study of readily removed substances of the stigmatic surface was initiated after a series of wide cross-pollinations among unrelated plants had shown that pollen germinates only rarely on the stigmas of unrelated species (Martin, unpublished). In contrast, many pollens germinate

Franklin W. Martin

Papers

Nutritional composition of okra seed meal

Okra, potential multiple-purpose crop for the temperate zones and tropics

Chromosome Numbers and Behavior in Some Species of Dioscorea

Self- and Interspecific Incompatibility in the Convolvulaceae

Compounds from the stigmas of ten species