Eckhard Wollenweber

Bio: Eckhard Wollenweber is an academic researcher from Technische Universität Darmstadt. The author has contributed to research in topics: Exudate & Flavonols. The author has an hindex of 31, co-authored 235 publications receiving 4301 citations. Previous affiliations of Eckhard Wollenweber include Gifu Pharmaceutical University & Braunschweig University of Technology.

Flavones and Flavonols

Abstract: Most reports on the identification of known flavonoids in new plant sources as well as those on novel flavonoids naturally deal with the two most abundant classes, the flavones and flavonols. For this chapter we have listed all references to the occurrence of flavone and flavonol aglycones which have appeared from 1975 to 1980, and also include such earlier references as were overlooked in the relevant chapters of The Flavonoids’ (1975). Emphasis is given to the natural distribution of these compounds. The data are collected in Tables 4.1 and 4.2 which cite substances, plant sources and references. Since 1974, some 50 flavones and 60 flavonols with common substitution patterns have been described as novel compounds. Many are simply new methyl ethers of known compounds. The structures are arranged throughout the Tables by number and arrangement of substituents in ring A, followed by ring B. Wherever possible, the plant organs from which the compounds have been isolated are cited. In cases where authors have extracted the ‘whole plant’ or ‘aerial parts’, it does not necessarily follow that the compound is present in all parts, since these substances are often specifically located in certain organs only. In all cases where free aglycones are encountered, especially highly methylated flavonoids, it is likely that they occur externally, or are associated with secretory structures and are correlated with the production of other lipophilic secondary compounds, mainly of terpenoid origin.

Propolis allergy. (I). Origin, properties, usage and literature review.

Abstract: Propolis or bee-glue, a resinous bee-hive product, is the cause of an increasing number of cases of allergic contact dermatitis. Formerly only observed in bee-keepers, propolis allergy today is mainly seen in individuals who use propolis in bio-cosmetics and self treatment of various diseases. Nearly 200 cases are summarized in an overview, including the first description of 'poplar bud' contact dermatitis from 1887. As practically all flavonoid aglycones and most of the other phenolics present in propolis are identical with the bud secretion of poplars, evidence is given that the poplar bud constituents are responsible for propolis hypersensitivity.

Propolis allergy. (II). The sensitizing properties of 1,1-dimethylallyl caffeic acid ester.

Abstract: As shown in the preceding paper, propolis or bee-glue is the cause of an increasing number of allergic reactions in persons using it in external preparations and cosmetics. Propolis and its main contact allergen, 1,1-dimethylallyl caffeic acid ester, designated LB-1, show strong sensitizing properties in patients as well as in guinea pig experiments. 9 patients have been patch tested with this compound, 8 of whom reacted strongly. Chemical separation of different propolis samples and poplar bud extracts reveal that LB-1 is always present. Poplar bud secretion is the bee's major source for propolis and hence the origin of LB-1. A warning is indicated, in agreement with several other authors, that propolis should not be used in topical products because of its strong sensitizing properties.

Chemistry and Biological Activities of Flavonoids: An Overview

Abstract: There has been increasing interest in the research on flavonoids from plant sources because of their versatile health benefits reported in various epidemiological studies. Since flavonoids are directly associated with human dietary ingredients and health, there is need to evaluate structure and function relationship. The bioavailability, metabolism, and biological activity of flavonoids depend upon the configuration, total number of hydroxyl groups, and substitution of functional groups about their nuclear structure. Fruits and vegetables are the main dietary sources of flavonoids for humans, along with tea and wine. Most recent researches have focused on the health aspects of flavonoids for humans. Many flavonoids are shown to have antioxidative activity, free radical scavenging capacity, coronary heart disease prevention, hepatoprotective, anti-inflammatory, and anticancer activities, while some flavonoids exhibit potential antiviral activities. In plant systems, flavonoids help in combating oxidative stress and act as growth regulators. For pharmaceutical purposes cost-effective bulk production of different types of flavonoids has been made possible with the help of microbial biotechnology. This review highlights the structural features of flavonoids, their beneficial roles in human health, and significance in plants as well as their microbial production.

Chemistry and Biochemistry of Dietary Polyphenols

Abstract: Polyphenols are the biggest group of phytochemicals, and many of them have been found in plant-based foods. Polyphenol-rich diets have been linked to many health benefits. This paper is intended to review the chemistry and biochemistry of polyphenols as related to classification, extraction, separation and analytical methods, their occurrence and biosynthesis in plants, and the biological activities and implications in human health. The discussions are focused on important and most recent advances in the above aspects, and challenges are identified for future research.