Potential usefulness of Mediterranean diet polyphenols against COVID-19-induced inflammation: a review of the current knowledge

Abstract

The Mediterranean diet is a dietary pattern typical of the populations living in the Mediterranean basin during the 50s-60s of the last century. This diet has demonstrated beneficial effects in the prevention of several pathologies such as cardiovascular diseases, metabolic syndrome, or several cancer types, at least in part, due to its antioxidant compounds. Since the COVID-19 pandemic started, different authors have been studying the effects of certain dietary habits on the presence of COVID-19 and its severity, and the Mediterranean diet is one of them. This review gathers data from studies supporting the potential usefulness of the main phenolic compounds present in the Mediterranean diet, based on their antioxidant and anti-inflammatory effects, as preventive/therapeutic agents against COVID-19. The current evidence supports the potential benefits that hydroxytyrosol, resveratrol, flavonols such as quercetin, flavanols like catechins, and flavanones on the order of naringenin could have on COVID-19. This is due to the increase in the synthesis and translocations of Nrf-2, which increases the activity of antioxidant enzymes and thus reduces ROS production, the scavenging of free radicals, and the suppression of the activity of MMP-9, which is involved in the cytokine storm, and the inhibition of NF-κB.

Keywords: Antioxidants; COVID-19; Mediterranean diet; Polyphenols.

Fig. 1

Proinflammatory response to the infection with SARS-CoV2. ACE2 receptor becomes unavailable to bind to Angiotensin II after viral infection. ACE, angiotensin-converting enzyme; AT1R, angiotensin II receptor type 1; G-CSF, granulocyte colony-stimulating factor; IL, interleukin; IP10, interferon gamma-induced protein 10; MAPK, mitogen-activated protein kinase; MCP1, monocyte chemoattractant protein 1; MIP1, macrophage inflammatory protein 1; S, spike glycoprotein; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; TNF-α, tumour necrosis factor α

Fig. 2

Potential protective effects of hydroxytyrosol against SARS-CoV-2-induced damage in alveolar tissue through anti-inflammatory mechanisms. The red plus symbols represent the damage induced by SARS-CoV-2 in lung tissue. The green minus symbols represent the processes suppressed by hydroxytyrosol. The truncated green lines represent the processes suppressed by hydroxytyrosol. HT, hydroxytyrosol; COX-2, cyclooxygenase-2; MMP-9, matrix metallopeptidase-9; NF, neutrophil; SARS-CoV-2; severe acute respiratory syndrome coronavirus 2

Fig. 3

Main potential protective effects of resveratrol against SARS-CoV-2-induced damage trough antioxidant and anti-inflammatory mechanisms. The red minus symbols and the truncated lines represent the processes suppressed by resveratrol. The green plus symbols and the arrows represent the processes activated by resveratrol. Keap1, Kelch-like ECH-associated protein 1; NF-κB, nuclear factor κB; Nrf2, factor nuclear erythroid 2; Nox, NADPH oxidases; ROS, reactive oxygen species; Sirt1, sirtuin 1

Fig. 4

Potential protective effects of EGCG against SARS-CoV-2-induced hyper-inflammation. The black arrows represent the signalling pathways activated. The truncated red lines represent the processes suppressed by EGCG. EGCG, epigallocatechin-3-gallate; IL-1β, interleukin-1β; IL-1 R, interleukin-1β receptor; IL-6, interleukin-6; IL-6 R, interleukin-6 receptor; IL-8, interleukin 8; JAK, Janus kinase; NF-κB, nuclear factor κB; STAT-3, signal transducer and activator of transcription protein 3; TAK-1, TGFβ-activated kinase 1; TNF-α, tumour necrosis factor α; TRAF-6, TNF-receptor-associated factor 6

Fig. 5

Potential mechanism of action of naringenin against SARS-CoV-2. ACE2, angiotensin-converting enzyme 2 receptor; 3CLpro, 3-chymotrypsin-like cysteine protease; NF-κB, nuclear factor κB; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2