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Chemopreventive Agents
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
However, it is important to appreciate the magnitude of the challenge in trying to understand the details of how a particular chemopreventive agent or its close analogues may inhibit the transition of a healthy cell into a tumor cell, or the growth and development of a small tumor once it is established. To illustrate this challenge, it is instructive to look at the literature relating to the flavonols, a group of reported chemopreventive compounds containing the 3-hydroxy-2-phenylchromen-4-one core, key members of which included quercetin, kaempferol, casticin, and galangin (Figure 12.2). Although all flavonols contain the 3-hydroxyflavone backbone, family members vary depending on the position of phenolic -OH groups. Flavonols of this type are found in a variety of vegetables such as onions, tomatoes, and broccoli, with an estimated intake in Western diets averaging 20–50 mg per day, and are also present in some fruits. Chemical structures of the parent flavonol structure, and the family members quercetin, kaempferol, casticin, and galangin.
Structure-Function Elucidation of Flavonoids by Modern Technologies
Published in Dilip Ghosh, Pulok K. Mukherjee, Natural Medicines, 2019
Ritu Varshney, Neeladrisingha Das, Rutusmita Mishra, Partha Roy
Flavonols have a 3-hydroxyflavone backbone (Figure 3.4). The different positions of the –OH group in the backbone is the only reason for the chemical diversity of this group. As far as flavonols in human diets are concerned, these are mainly found in vegetables, fruits and beverages like tea and wine (Hertog et al. 1993; Crozier et al. 1997; McDonald et al. 1998). Some of the widely studied flavonols are discussed below.
Anti-Cancer Agents from Natural Sources
Published in Rohit Dutt, Anil K. Sharma, Raj K. Keservani, Vandana Garg, Promising Drug Molecules of Natural Origin, 2020
Debasish Bandyopadhyay, Felipe Gonzalez
Flavonols contain 3-hydroxy-2-phenylchromen-4-one pharmacophore having 3-hydroxyflavone backbone. They are commonly found in certain teas, berries, and wines. Their exact quantity (amount) greatly depended on particular species and regional climate. Perhaps the most common flavonol compounds are quercetin and kaempferol (Figure 5.16). Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is found in abundance in apples, honey, and citric fruits. Recent studies conducted on quercetin indicated its ability to combat cancers through multi-targeted mechanisms (Erlund et al., 2004; Hendriks et al., 2003; Ramos, 2007). In various controlled concentrations, quercetin was able to overturn growth of the malignant tumor in ovarian, lung, colorectal, and breast cancers. Furthermore, daily intake of quercetin might be cancer-preventive. In one study, quercetin was validated, in vitro and animal model, on nine different malignant cells that involved CT-26 (colon carcinoma), LNCap (prostate carcinoma), PC3 (prostate adenocarcinoma), PC12 (adrenal medulla from rat), MCF-7 (breast carcinoma). U266B1 (B lymphocyte), Raji (B lymphocyte), CHO (epithelial ovary cells from Chinese hamster), and MOLT-4 (leukemia T lymphoblast). Studies concluded that quercetin-initiated apoptosis in CT-26, LNCaP, MOLT-4, and Raji in various concentrations. Animal models were subjected for CT-26 and MCF-7 malignancies since they demonstrated a higher sensitivity to quercetin. In animal model CT-26 and MCF-7 tumor growths were principally reduced although it could not prevent PC3 and CHO cell growth even at strong concentrations (Jakubowicz-Gil et al., 2005). Kaempferol, a similar flavonol compound, works in a similar manner. Kaempferol (3,4′,5,7-tetrahydroxyflavone), originated in the coniferophyte family, could prevent malignant cell growth as reported recently. In these experiments, kaempferol successfully regulated cyclin-dependent kinase1 (CDK1), cyclin B, and p53 in MCF-7 and HeLa malignancies (Hashemzaei et al., 2017; Xu et al., 2008). Cyclin B binds to CDK1 to form a maturation promoting factor (MPF). This MPF promotes the transition of G2 to M phase in cell cycle. By regulating CDK1 and cyclin B, kaempferol can initiate apoptosis to occur in cancerous cells. In a different study, conducted on U-2 OS osteosarcoma cells (bone cancer cells), kaempferol suppressed transcription factors AP-1 and ERK p38 which inhibited cancer metastasis (Chen et al., 2001).
Phenolic composition, antioxidant activity, anticholinesterase potential and modulatory effects of aqueous extracts of some seaweeds on β-amyloid aggregation and disaggregation
Published in Pharmaceutical Biology, 2019
Tosin A. Olasehinde, Ademola O. Olaniran, Anthony I. Okoh
LC-MS chromatograms revealed different peaks representing different compounds as shown in Figure 1(A-D). Phenolic compounds such as phlorotannins, flavonoids and phenolic acids were identified in the macroalgal extracts (Table 1). Phloroglucinol was the only phlorotannin identified in ECK-AQ, RED-AQ and URL-AQ but was absent in GEL-AQ (Tables 1–4). Rutinose and 1-caffeoyl-4-deoxyquinic acid as well as 3-hydroxyflavone were identified in ECK-AQ and were not present in other extracts (Table 1). Furthermore, phenolic acids such as vanillic and syringic acids were identified in GEL-AQ (Table 2). Flavonoids such as epicatechin-3 glucoside and catechin were identified in ECK-AQ and GEL-AQ (Tables 1 and 2). However, RED-AQ contains epicatechin-3 glucoside, while URL-AQ had catechin (Tables 3 and 4). Furthermore, myricetin and taxifolin that is also referred to as dihydroquercetin were present in URL-AQ but not in other seaweed extracts (Table 4). Other flavonoids present in the extracts include quercetin, 3,7-dimethyl quercetin, 5,7-dimethoxyflavone, 3,5,7-trimethylfavone and biochanin A.