Abstract

Soybeans are rich in proteins and lipids and have become a staple part of the human diet. Besides their nutritional excellence, they have also been shown to contain various functional components, including isoflavones, and have consequently received increasing attention as a functional food item. Isoflavones are structurally similar to 17-β-estradiol and bind to estrogen receptors (ERα and ERβ). The estrogenic activity of isoflavones ranges from a hundredth to a thousandth of that of estrogen itself. Isoflavones play a role in regulating the effects of estrogen in the human body, depending on the situation. Thus, when estrogen is insufficient, isoflavones perform the functions of estrogen, and when estrogen is excessive, isoflavones block the estrogen receptors to which estrogen binds, thus acting as an estrogen antagonist. In particular, estrogen antagonistic activity is important in the breast, endometrium, and prostate, and such antagonistic activity suppresses cancer occurrence. Genistein, an isoflavone, has cancer-suppressing effects on estrogen receptor-positive (ER+) cancers, including breast cancer. It suppresses the function of enzymes such as tyrosine protein kinase, mitogen-activated kinase, and DNA polymerase II, thus inhibiting cell proliferation and inducing apoptosis. Genistein is the most biologically active and potent isoflavone candidate for cancer prevention. Furthermore, among the various physiological functions of isoflavones, they are best known for their antioxidant activities. S-Equol, a metabolite of genistein and daidzein, has strong antioxidative effects; however, the ability to metabolize daidzein into S-equol varies based on racial and individual differences. The antioxidant activity of isoflavones may be effective in preventing dementia by inhibiting the phosphorylation of Alzheimer’s-related tau proteins. Genistein also reduces allergic responses by limiting the expression of mast cell IgE receptors, which are involved in allergic responses. In addition, they have been known to prevent and treat various diseases, including cardiovascular diseases, metabolic syndromes, osteoporosis, diabetes, brain-related diseases, high blood pressure, hyperlipidemia, obesity, and inflammation. Further, it also has positive effects on menstrual irregularity in non-menopausal women and relieving menopausal symptoms in middle-aged women. Recently, soybean consumption has shown steep increasing trend in Western countries where the intake was previously only 1/20–1/50 of that in Asian countries. In this review, Ihave dealt with the latest research trends that have shown substantial interest in the biological efficacy of isoflavones in humans and plants, and their related mechanisms.

Highlights

  • Substances that interfere with the endocrine system are known as endocrine disruptors

  • Isoflavones were shown to reduce the liver index that had increased due to the high-fat diet as well as the serum biochemistry levels [alanine aminotransferase (ALT), aspartate aminotransferase (AST), low-density lipoprotein (LDL)-cholesterol, triglycerides, and total cholesterol] and to increase free fatty acids and high-density lipoprotein (HDL)-cholesterol that had been reduced by the alcohol (Table S4) [78]

  • The results showed that soy flavanone and hop prenylflavanone (Soy-Hop) intake significantly inhibited estrogen deficiency-induced increases in body weight, fat mass, leptin, LDL-cholesterol, total cholesterol, triglycerides, and glucose and insulin circulation

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Summary

Introduction

Substances that interfere with the endocrine system are known as endocrine disruptors. Antioxidants 2021, 10, 1064 and lariciresinol), isoflavones (genistein, daidzein, glycitein, and formononetin), coumestans (coumestrol), and prenylflavonoids [3] Such phytoestrogens are abundant in grains, vegetables, and fruits. Genistein and daidzein in particular been attracting attention for their anti-cancer and antioxidative effects, and are hypothesized to have the potential to prevent and treat various types of cancers, and various lifestyle diseases [9,13]. They have been found to inhibit the action of enzymes involved in the proliferation of cancer cells; several studies have reported their ability to inhibit cancers such as prostate cancer. I hope that this review will be helpful to a wide range of readers, including persons or researchers broadly interested in natural science, agriculture, food science, or medicinal foods

Search Strategy
Isoflavone Biosynthesis and Regulation
Structure and Type of Isoflavones
Functionality of Isoflavones in Plants
Estrogen-Like Effect and Activity
Neuroprotective Effect and Improvement of Cognitive Impairment
Antidepressant Effects
Anti-Obesity Effects
Effects on Improving Metabolic Syndrome
Improvements of Blood Pressure
Improvement of Cardiac Function
Protection against Liver Damage
4.10. Improvement of Renal Dysfunction
4.11. Anti-Inflammatory Effects
4.12. Anticarcinogenic Activity through Gene Regulation
4.13. Promotion of Osteogenesis and the Prevention of Osteoporosis
4.14. Improvement of Blood Glucose Homeostasis
4.15. Reduced Inflammation and Skin Cell Protection in Wound Tissue
4.17. Safety of Isoflavones in Reproductive Development
4.18.2. Antioxidant Activity
4.18.3. Antiviral Effect
4.18.4. Allergy Relief
4.19. Other Considerations
4.20. Side Effects
Conclusions
Findings
Perspectives
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