Quercetin is an increasingly well-known member of the group of Polyphenols and Flavonoidswhich are natural dyes characterised in particular by their light yellow colour (from the Latin flavus; yellow). Flavonoids are biologically active plant compounds that have, for example, antioxidant and anti-inflammatory effects in humans. However, the body cannot produce quercetin itself and therefore absorbs it through food. A normal western diet contains about 15 mg to 40 mg quercetin daily.

Quercetin occurrence

The name quercetin is derived from the Latin word Quercētum, which means oak forest and underlines the plant origin. Larger amounts of the molecule are found in, for example, capers (234 mg per 100 g) and onions (11-33 mg per 100 g), apples and berries (both 2-5 mg per 100 g), and various teas (black tea 2 mg per 100 g). Quercetin accumulates mainly in the outer parts of the plant. In apples, it accumulates in the skin.

Cellular senescence

The term senolysis is composed of the two words senescence and lysis. While lysis is understood to mean dissolution or decay, the first part of the word tells us exactly what we are talking about. Senescence(from the Latin senescere; to age) plays an important role as the final stage of dozens of processes in the body.

Cellular senescence refers to a stable arrest of the cell cycle. Human cells can only complete a limited number of cell divisions before they suddenly stop and age. What is common today was once groundbreaking. Decades ago, science believed that all cells were immortal. Today we know that cancer cells in particular possess this characteristic. The phenomenon of the division ceiling is called replicative senescence, or after its discoverer: Hayflick limit. With increasing age, the number of senescent cells steadily increases, because too many of these dormant cells are produced and, on the other hand, too few are degraded.

Quercetin as a Trojan horse

This dormant state sounds harmless and not very worrying at first. However, senescent cells can "infect" surrounding healthy cells and thus retire them prematurely. Certain substances produced by aged cells are responsible for this and are subsumed under the term "secretome". Aged cells also defend themselves against apoptosis, the natural cell death, by activating survival-promoting factors and inhibiting self-destructive signals.

Senolytically active substances such as quercetin are smuggled into the cell past the protective shield and can switch off the defence shield there from the inside. This happens by blocking an enzyme called PI3 kinase. This interrupts the chain that promotes survival and the senescent cell can die in a controlled manner and make room for new cells.

Results of initial laboratory studies are promising and give many scientific eyes a glimmer of hope. However, large-scale human studies are still needed to confirm the results and make further statements.