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Herbs in Cancer Therapy
Published in Anil K. Sharma, Raj K. Keservani, Surya Prakash Gautam, Herbal Product Development, 2020
Annum Malik, Shahzadi Sidra Saleem, Kifayat Ullah Shah, Learn-Han Lee, Bey Hing Goh, Tahir Mehmood Khan
Flavonoids, or bioflavonoids, include about 3000 natural phenolic structures. They commonly occur in almost every vegetable, fruit, and herb. They are also found in tea and coffee. Flavonoids constitute a considerable part of our daily dietary value, mostly in the form of quercetin (Kühnau 1976). They act as anti-inflammatory, enzyme inhibitors, that can potentially improve capillary resistance and battle free radicals. Flavonoids are classified into flavanones, flavones, isoflavones, flavonols, flavanols, and anthocyanidins. Flavanones have limited distribution, found mainly in citrus fruits such as lemons and oranges (Hollman et al. 1997). Flavones are widely distributed, such as luteolin and apigenin. Isoflavones include genistein, which can potentially inhibit human prostate cancer cells, and daidzein. Food rich in isoflavones includes legumes such as soy. Flavonols are found as naturally occurring glycosides, and the major ones include kaempferol and quercetin. Flavanols, or flavan-3-ols, have limited distribution and are found in tea, apples, broccoli, etc. Catechins such as epigallocatechin gallate (EGCG) are an example of flavanols. Anthrocyanidins are red-blue pigments found in berries. They are responsible for pigmentation in fruits.
Microbial Biofilms-Aided Resistance and Remedies to Overcome It
Published in Bakrudeen Ali Ahmed Abdul, Microbial Biofilms, 2020
They are usually known as plant phenolics and are derived from amino acid phenylalanine and tyrosine. They possess a phenyl ring with a propane side chain. They are classified into hydroxycinnamic acid, coumarins, lignans, and flavonoids. Plant extracts are found to be rich in flavonoids. These flavonoids themselves are sub-classified into flavanol, flavanone, isoflavone, flavone, flavan-3-ols or catechin, and anthocyanin. The mode of action of flavonoids includes interaction with bacterial proteins and cell wall structures thus inhibiting nucleic acid, cell wall synthesis, or energy metabolism (Lahiri et al. 2019). Moreover, they also interfere with bacterial signaling within the biofilm by inhibiting N-acyl homoserine lactones-mediated QS (Górniak et al. 2019). Table 16.1 highlights the antibiofilm potentials of different flavonoids.
Potential Use of Bioactive Compounds from Waste in the pharmaceutical Industry
Published in Quan V. Vuong, Utilisation of Bioactive Compounds from Agricultural and Food Waste, 2017
Flavonols (quercetin, kaempferol and myricetin, for example) are the most widespread of the flavonoids found in vegetables, like onions, broccoli, apples, cherries and berries, tea and red wine. These compounds have anti-mutagenic, anti-carcinogenic and anti-hypertensive effects. Isoflavones (genistein, daidzein and coumestrol, for example) are found almost exclusively in leguminous plants such as soybean. They can exert pro- and anti-oestrogenic effects. Flavan-3-ols (include catechins and the larger proanthocyanidins) are found in tea, apples, apricots, cherries, red wines and dark chocolate. Flavones (apigenin and luteolin) are found in parsley, thyme and celery, for example. Anthocyanidins are mainly present in plants like anthocyanins, that are attached to sugar molecules. They are responsible for the characteristic red, blue and purple colored flowers, berry fruits and red wine. Flavanones are contained in citrus fruits (hesperetin in citrus peel; naringenin in grapefruit peel, imparting a bitter flavor) (Denny and Buttriss 2007).
Theoretical investigation on the structure and antioxidant activity of (+) catechin and (−) epicatechin – a comparative study
Published in Molecular Physics, 2020
S. Anitha, S. Krishnan, K. Senthilkumar, V. Sasirekha
Flavan-3-ols are one of the important class of flavonoids identified in grapes, green tea, blue berries and cocoa [18–21]. The antioxidant activity of the flavan-3-ols is related to their structural properties. Flavan-3-ols (flavanols) are characterised by resorcinol and catechol moiety, namely A ring and B ring, that are interconnected by Pyron ring (C ring) [22,23] refer Figure 1. The radical scavenging properties of flavan-3-ols depend mainly on the distribution of hydroxyl groups and its H-atom donating capacity [24]. The stability of phenoxy radical generated after hydrogen atom transfer (HAT) also contributes to their scavenging action against reactive oxygen radicals [25,26]. Based on the projection angle of a hydroxyl group bonded to C ring at C3 atom and projection angle of B ring bonded to C ring at C2 atom, catechin has four diastereoisomers, namely (+) catechin (2R,3S), (−) epicatechin (2R,3R), (−) catechin (2S,3R) and (+) epicatechin (2S,3S) [27]. The numbers in the bracket proceeding names of the structure are indicative of site of a projected bond, while R refers to dashed wedge bonds (bonds that are projecting out of paper away from the viewer) and S refers to solid wedge bond (bonds that projects out of paper towards the viewer), refer Figure 2. Among these four stereoisomers, (+) catechin (CT a trans-isomer) and (−) epicatechin (ECT a cis isomer) are the most important naturally occurring flavan-3-ols that are present in grape seed [28–30]. CT and ECT are main monomers characterised by their tendency to form complex structures, namely procyanidins. Their antioxidant properties also depend on the degree of polymerisation [31]. The radical scavenging ability of CT and ECT is due to their structural characteristics, such as dihydroxyl group at C-3’ and C-4’ on the B ring, C3-hydroxyl group on C ring with the absence of 2, 3 double bond, and C5, C7 hydroxyl groups on ring A. Here, catechol ring (B) has high electron-donating ability compared to other rings due to the presence of ortho-dihydroxyl group [32–35].