Ursolic acid is a pentacyclic triterpenoid compound found abundantly in the plant kingdom, especially in the skin of fruits. Emerging research suggests ursolic acid may have anti-inflammatory, antioxidant, and antidisease properties that could benefit human health. Apples with skin intact contain ursolic acid, but levels can vary significantly among different varieties. This article will explore the concentration of ursolic acid in apples, how it compares to other fruits, the potential effects of cooking and processing, and the possible health implications of ingesting apple-derived ursolic acid.
What is Ursolic Acid?
Ursolic acid belongs to the family of triterpenes - compounds synthesized by plants that are derived from six isoprene units. It is widely found in fruits like apples, cranberries, prunes and olives as well as herbs like oregano, thyme, lavender and rosemary. Ursolic acid has generated interest for its biological effects as an antioxidant that reduces oxidative damage and inflammation. Research indicates ursolic acid can inhibit some pro-inflammatory signaling pathways and enzymes like COX-2. It also demonstrates antiproliferative activities that suppress growth and proliferation of certain disease cells. While studies thus far have been limited to cell cultures and animal models, ursolic acid shows promise in helping prevent chronic diseases and possibly treating diseases.
Do Apples Have Ursolic Acid?
Yes - all varieties of apples contain some level of ursolic acid, specifically concentrated in the skin and peel. However, there is considerable variability in concentrations among different cultivars. One study analyzing 72 apple cultivars found total ursolic acid content ranging from 2-39 mg per 100 grams fresh fruit weight. The top 10 highest ranking apples contained 29-39 mg ursolic acid per 100 g. In general, apples with thicker, more intensely colored and matte skins (like Red Delicious) have more ursolic acid than thin-skinned varieties (like Golden Delicious). Heirloom and wild varieties also tend to be higher than commercial types. Testing has shown levels decline as apples ripen. So firmer, under-ripe apples have slightly more ursolic acid than mature, ready-to-eat fruits. Nonetheless, apples remain one of the most abundant dietary sources of ursolic acid.
Health Benefits of Ursolic Acid
Though still an emerging area of research, early evidence suggests ursolic acid powder intake may support human health. As an antioxidant, ursolic acid neutralizes cell-damaging free radicals and reduces markers of oxidative stress. It also inhibits pro-inflammatory cytokines, enzymes and pathways linked to chronic inflammation. Via these antioxidant and anti-inflammatory activities, greater ursolic acid intake has been associated with reduced risk and severity of obesity, metabolic disorders, neurological decline, heart disease and diabetes in animal model studies. Separate research indicates ursolic acid can suppress growth of diverse disease cell types and even induce programmed cell death (apoptosis) in lung, breast, bladder and skin diseases. While human clinical trials are still lacking, the preliminary data implies ursolic acid may help prevent or slow the progression of various inflammatory diseases and age-related conditions.
What Fruits are High in Ursolic Acid?
After apples, olives and cranberries emerge as the next richest dietary sources of ursolic acid. 100 g of raw cranberries contains up to 14.5 mg ursolic acid. Extra virgin olive oil contains 5-14 mg per 100 g. Blueberries, plums, prunes, basil and oregano also provide over 5 mg per 100 g serving. Overall, the edible skins of fruits tend to concentrate more ursolic acid - hence fruits like strawberries and grapes having lower levels since we don't typically eat their skins. Comparing ursolic acid on a fresh weight basis, 100 g whole apples provide much more (as high as 39 mg) than other common portions of fruit. And since we often enjoy apples including the antioxidant-rich skins, they remain one of richest and most practical ways to consume apple peel powder ursolic acid in our diets.
Cooking and Processing Effects
Since ursolic acid accumulates in apple peels, processing and cooking techniques that remove the peel also reduce the content in the final products. Applesauce containing crushed skins retains more ursolic acid than peeled slices or juice alone. One study testing the microwave cooking of apples found 77% ursolic acid content retained after 2 minutes, 56% after 4 minutes and 53% after 6 minutes. Warm pasteurized apple cider maintains high levels similar to raw juice, while harsher distillation into apple brandy and vinegar removes nearly all ursolic acid initially present. Considering most dietary guidelines emphasize eating whole produce over juices due to fiber and nutrient losses, consuming whole raw apples seems the best way to obtain the original ursolic acid content.
What Does Ursolic Acid Do to the Liver?
A handful of studies injecting or feeding ursolic acid to rodents have observed protective effects in the liver. In mice with chemically-induced liver damage resembling human non-alcoholic fatty liver disease, ursolic acid improved liver structure, function and healed injury by reducing fat accumulation, oxidative stress and inflammation. This may relate to the interaction between ursolic acid and skeletal muscle tissue. Some research found increased skeletal muscle mass in mice treated with high dose injections of ursolic acid compared to control groups. While evidence appears promising that ursolic acid supports normal, healthy liver function, more research is still needed - especially clinical human studies on realistic oral doses from edible fruits like apples.
Dietary Recommendations
While research has yet to determine an optimal daily intake level for ursolic acid, regular apple consumption may provide valuable amounts, especially for adults not meeting minimum fruit intake recommendations. Given associations between apple flavonoids like quercetin and benefits for heart health plus potential additive or synergistic effects with other apple phytonutrients, enjoying whole fresh apples should come as part of balanced fruit intake and overall healthy dietary pattern. Those looking to leverage possible anti-inflammatory, antidisease or liver health benefits from ursolic acid powder might consume apples including peels to maximize exposure from this source. However, supplements attempting to isolate or concentrate ursolic acid remain premature without more evidence on efficacy and safety for humans.
Ursolic acid stands out as a phytonutrient of interest in one of America’s most widely consumed fruits - the apple. Early research highlighting anti-inflammatory, antioxidant and potential antidisease mechanisms continues to build the case that ursolic acid from whole food sources like apples may support human health. While varietal, seasonal and maturity differences affect concentrations, apple lovers can continue enjoying this beloved fruit as a practical way to obtain dietary ursolic acid. Considering emerging data around apple nutrients and moderate evidence on ursolic acid alone, whole fresh apples eaten in their entirety with skins intact perhaps best capture any synergistic combination of effects with the lowest risk.
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References:
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2. Li Y, Yao J, Han C, et al. Quercetin, Inflammation and Immunity. Nutrients. 2016;8(3):167. doi:10.3390/nu8030167
3. Aumsuwan P, Khan SI, Khan IA, et al. Ursolic acid: A review of its diverse biological activities. Int J Mol Sci. 2019;20(9):1-27. doi:10.3390/ijms20092191
4. Liu W, Wang H, Wang Y, et al. Ursolic acid induces apoptosis through mitochondrial intrinsic pathway and suppression of ERK1/2 MAPK in HeLa cells. J Pharm Pharmacol. 2013;65(7):1095-1104. doi:10.1111/jphp.12083
