Dietary Phenolic Compounds: Their Health Benefits and Association with the Gut Microbiota

Abstract

Oxidative stress causes various diseases, such as type II diabetes and dyslipidemia, while antioxidants in foods may prevent a number of diseases and delay aging by exerting their effects in vivo. Phenolic compounds are phytochemicals such as flavonoids which consist of flavonols, flavones, flavanonols, flavanones, anthocyanidins, isoflavones, lignans, stilbenoids, curcuminoids, phenolic acids, and tannins. They have phenolic hydroxyl groups in their molecular structures. These compounds are present in most plants, are abundant in nature, and contribute to the bitterness and color of various foods. Dietary phenolic compounds, such as quercetin in onions and sesamin in sesame, exhibit antioxidant activity and help prevent cell aging and diseases. In addition, other kinds of compounds, such as tannins, have larger molecular weights, and many unexplained aspects still exist. The antioxidant activities of phenolic compounds may be beneficial for human health. On the other hand, metabolism by intestinal bacteria changes the structures of these compounds with antioxidant properties, and the resulting metabolites exert their effects in vivo. In recent years, it has become possible to analyze the composition of the intestinal microbiota. The augmentation of the intestinal microbiota by the intake of phenolic compounds has been implicated in disease prevention and symptom recovery. Furthermore, the “brain–gut axis”, which is a communication system between the gut microbiome and brain, is attracting increasing attention, and research has revealed that the gut microbiota and dietary phenolic compounds affect brain homeostasis. In this review, we discuss the usefulness of dietary phenolic compounds with antioxidant activities against some diseases, their biotransformation by the gut microbiota, the augmentation of the intestinal microflora, and their effects on the brain–gut axis.

Dietary (Poly)phenols and Cognitive Decline: A Systematic Review and Meta‐Analysis of Observational Studies

“…[ 73 ] Intake of (poly)phenol‐containing foods has been shown to increase Bifidobacterium , Enterococcus , and Lactobacillus strains and improve the overall balance of intestinal microbes. [ 74 ] The intestinal flora per se may play a role in the host nervous system's health through the gut‐brain axis and eventually affect cognitive function. [ 75 ] For instance, metabolites generated by the gut microbiota, including short‐chain fatty acids, aromatic amino acids, trimethylamine‐ N ‐oxide, urolithin A, equol, imidazole, and propionate are known to maintain intestinal homeostasis and regulate neuro‐immunoendocrine function.…”

Chia Phenolic Extract Appear to Improve Small Intestinal Functionality, Morphology, Bacterial Populations, and Inflammation Biomarkers In Vivo (Gallus gallus)

“…Phenolic compounds can reach the colon, serving as a substrate for the resident microbiota; after they are absorbed and circulated in the body, they can exert a wide range of effects in the intestine, such as anti-inflammatory effects [ 1 , 33 , 34 , 35 ]. In this present study, we aimed to assess the impact of the intra-amniotic administration of a phenolic extract from chia seeds.…”

“…Moreover, these compounds contribute to several sensory attributes of plants, including color, flavor, and astringency. Their consumption has exhibited preventive effects against conditions such as obesity, cardiovascular disorders, diabetes, and neurodegenerative diseases [ 1 , 2 , 3 , 4 ].…”

“…Due to their bioavailability, the effects of phenolics are related to the food matrix, depending on whether they are consumed in the whole food or as isolated compounds [ 5 , 15 , 16 , 17 ]. However, the effects of isolating phenolic extracts on gut health, nutrient digestibility, absorption of some vitamins and minerals, and gut microbiota may differ depending on their dosage [ 1 , 18 ]. Therefore, phenolic compounds and other bioactive compounds from food sources need to have their effects and safety validated in in vivo studies.…”

Potential Role of Dietary Phenolic Compounds in the Prevention and Treatment of Rheumatoid Arthritis: Current Reports

“…Indeed, because most chemical drugs possess several unwanted effects and are little active, many people prefer to use natural molecules [33]. Among the most promising molecules, phenolic compounds, including simple phenols (e.g., catechol, pyrogallol, phloroglucinol, and resorcinol) and polyphenols (e.g., coumarins, anthocyanins, lignans, and phenolic acids) seem to be promising therapeutic and/or adjuvant approaches (Figure 2) [50][51][52]. Simple phenolics have a low molecular weight, and most of them (except resorcinol) are rapidly absorbed by the human skin, while polyphenols are largely widespread and ubiquitous in nature, being largely found in several types of algae, beans, fruits, bark, herbs and spices, legumes, leaves, nuts, whole grains, oilseeds, and roots (Table 1) [53,54].…”