FLAVONOIDS: BIOCHEMISTRY, BIOPHYSICS, MEDICINE - Tarakhovsky Yu. S. - 2013

Introduction

Flavonoids belong to the Class of plant-derived polyphenolic compounds. They can be classified as secondary plant metabolites. However, among secondary metabolites, this group of substances is one of the most prominent due to its involvement in many key processes of Plant GROWTH AND DEVELOPMENT. Flavonoids are not only responsible for plant pigmentation and flower coloration; they play a significant role in Cell signaling pathways, acting as chemical messengers, and participate in plant reproduction—specifically in pollen development and function, nectar accumulation, and the ripening of fruits and seeds. Emerging evidence suggests that flavonoids may be involved in Gene Expression regulation, altering The activity of regulatory Proteins and influencing Cell Division. Nevertheless, the most prominent role of flavonoids lies in protecting plants from various adverse environmental factors, such as ultraviolet radiation, Temperature stress, and elevated heavy metal concentrations. Flavonoids play a crucial role in defending plants against bacterial, viral, and fungal infections, parasite invasion, and insect damage. One of their most notable Functions is protecting plants from oxidative stress owing to their potent antioxidant activity.

The Diversity of flavonoids is vast, encompassing approximately 8,000 distinct compounds. It is estimated that up to 20% of the carbon fixed during Photosynthesis is channeled into The production of polyphenolic compounds, with flavonoids occupying a substantial share. Flavonoids are not synthesized in animal and human Cells, and their presence in Tissues depends entirely on the Dietary intake of plant-derived foods. Hertog was among the first to estimate flavonoid intake across large populations. It was demonstrated that mortality from myocardial infarction among the elderly is inversely correlated with flavonoid intake. At the same time, this author found no significant association between flavonoid consumption and Cancer incidence. Subsequent long-term observational studies involving many thousands of volunteers did not consistently confirm a correlation between flavonoid intake and cardiovascular diseases. More recent studies investigating The Link Between flavonoid consumption and cancer have likewise yielded inconclusive results. The question of how flavonoids impact human health remains open to this day. Unlike recognized Vitamins—such as Vitamin E or Vitamin C—the absence of dietary flavonoids does not lead to a distinct deficiency syndrome. Consequently, classifying flavonoids under Vitamin P proved premature and was later abandoned.

Since the early 1990s, considerable attention has been paid to the so-called Mediterranean diet, following the discovery of a significantly lower incidence of cardiovascular diseases among certain Mediterranean populations. A reduction in inflammatory and oncological conditions, enhanced cognitive function, and a decreased risk of Alzheimer's disease and senile dementia were also observed. This phenomenon is generally attributed to dietary habits.

In 2010, UNESCO inscribed the Mediterranean diet on the Representative List of the Intangible Cultural Heritage of Humanity for Italy, Spain, Greece, and France (http://www.unesco.org/culture/ich/en/RL/00394). KEY FEATURES OF this diet include the consumption of unsaturated fats and vitamins. Some researchers attribute particular importance to the polyphenols present in olive oil, fruits, and red wine. There is a strong consensus among researchers regarding the positive Impact of plant polyphenols—particularly flavonoids—on human health. The World Health Organization (WHO) recommends a daily intake of at least 400 g of fruits and vegetables, which is estimated to potentially save up to 2.7 million lives annually by preventing certain cancers, cardiovascular diseases, obesity, and diabetes (see the WHO website: http://www.who.int/dietphysicalactivity/en/).

Interest in flavonoids is driven not only by their potential health benefits derived from plant-based diets, but also by the prospect of developing synthetic derivatives with therapeutic Applications. Flavonoids hold promise for the creation of novel, highly active drugs with anti-inflammatory, anticancer, antiviral, antiparasitic, or bactericidal properties. They are currently being used to develop and test new Antibiotics, as well as adjuvants that enhance the efficacy of other medications by inhibiting multi-drug resistance mechanisms. Recent studies have demonstrated that derivatives of certain flavonoids can be successfully employed in treating various internal organ disorders, often exhibiting higher efficacy than conventional Pharmaceuticals. Notably, flavonoids and their derivatives frequently display lower toxicity and fewer side effects than analogous drugs obtained from other sources. At the same time, it must be considered that the excessive consumption of any substance carries potential negative consequences. Flavonoids are no exception, although the Adverse effects of flavonoid overconsumption remain poorly understood. Particular caution should be exercised regarding high doses of purified flavonoid supplements marketed as dietary supplements.

In light of their therapeutic potential, there is currently a surge of interest in investigating the Effects of Flavonoids on The Human Body. Over the past two decades, the volume of research in this field has grown more tenfold, reaching approximately 5,000 publications per year (Fig. 1). This is roughly comparable to the number of publications on targeted drug delivery and is twice the number of publications on Gene Therapy. Flavonoids are discussed in the majority of studies analyzing The chemical composition of traditional medicinal plants, and their presence is frequently cited as the basis for the medicinal properties of specific herbs. Plant extracts rich in flavonoids, as well as isolated individual flavonoids, are widely investigated. Various attempts are being made to enhance the therapeutic properties of flavonoids through chemical modifications or by employing bioavailability-enhancement strategies. Despite extensive recent research, a clear understanding of the Mechanisms of action of these compounds remains elusive. It must be acknowledged that this scientific field is still in the data-accumulating stage, whereas The Development of a unified theoretical framework explaining flavonoid action remains a task for the future.

Fig. 1. Number of studies on flavonoids by year, according to PubMed data. The search was performed using the keyword "flavonoids" via Reference Manager.