Herbs (Global Traditional) · European
Caper (Capparis spinosa) (Capparis spinosa)
Moderate Evidencebotanical
Hermetica Superfood Encyclopedia
Caper (Capparis spinosa) contains quercetin and rutin as primary bioactive compounds that provide antioxidant and anti-inflammatory effects. These flavonoids help regulate blood glucose levels and reduce inflammatory markers through inhibition of pro-inflammatory cytokines.
Caper (Capparis spinosa L.) is a perennial shrub native to the Mediterranean region, parts of Asia, and North Africa, where its flower buds and fruits are harvested. The plant material is typically processed through hydroalcoholic extraction, ultrasound-assisted extraction for bioactive compounds like rutin, or salt fermentation for culinary use.
A randomized double-blind placebo-controlled trial (PMID: 24050578) in 54 type 2 diabetic patients found that 400 mg caper fruit extract three times daily for 2 months significantly reduced blood glucose and HbA1c. A systematic review and meta-analysis (PMID: 37806093) evaluated caper fruit's effects on metabolic markers, finding overall benefits, though human evidence remains limited to one key diabetes RCT.
Clinical studies used caper fruit extract at 400 mg three times daily (total 1,200 mg/day) for blood sugar management. Preclinical studies suggest 1-5 g/day equivalents, but these doses lack human validation. No standardized extract specifications were detailed in trials. Consult a healthcare provider before starting any new supplement.
Per 100g of drained canned capers: Energy ~23 kcal; Protein ~2.4g; Fat ~0.9g; Carbohydrates ~1.7g; Dietary fiber ~3.2g. Exceptionally high in sodium (~2,348mg, due to brining/salt-packing). Key micronutrients: Vitamin K ~24.6µg (31% DV), Vitamin C ~4.3mg, Riboflavin (B2) ~0.14mg, Niacin (B3) ~0.65mg, Iron ~1.67mg (9% DV), Copper ~0.37mg (41% DV), Magnesium ~33mg, Calcium ~40mg, Manganese ~0.08mg. Bioactive compounds: Exceptionally rich in quercetin (~180mg/100g dry weight, among the highest of any plant food) and its glycosides including quercetin-3-rutinoside (rutin, ~332mg/100g dry weight) and quercetin-3-rhamnoside; Kaempferol and kaempferol glycosides (~131mg/100g dry weight); Glucocapparin (a glucosinolate unique to Capparis, ~50–90mg/100g dry weight); Stachydrine (a proline betaine, ~0.2–0.8% dry weight, linked to anti-diabetic activity); Capparisine and other spermidine alkaloids; p-Methoxy benzoic acid; Tocopherols (primarily α-tocopherol, ~3–5mg/100g in buds); Indole-3-carbinol (trace amounts); Beta-carotene and lutein (small amounts contributing to antioxidant capacity). The seed oil (if consumed) contains oleic acid (~40%), linoleic acid (~30%), and minor amounts of stearic and palmitic acids. Bioavailability notes: Quercetin glycosides in capers have relatively high bioavailability compared to quercetin aglycone, as rutinoside forms are cleaved by gut microbiota to release quercetin for colonic absorption; however, brining and pickling may reduce total flavonoid content by 30–50% compared to fresh buds. Sodium content is significantly modifiable by rinsing before consumption. The glucosinolate glucocapparin undergoes hydrolysis by myrosinase upon tissue disruption, yielding methyl isothiocyanate, which may have bioactive properties but is partly lost during cooking.
Caper's quercetin and rutin compounds inhibit alpha-glucosidase enzyme activity, slowing carbohydrate absorption and reducing postprandial glucose spikes. These flavonoids also suppress NF-κB signaling pathway, decreasing production of inflammatory cytokines like TNF-α and IL-1β. Additionally, the antioxidant properties help neutralize reactive oxygen species and reduce oxidative stress markers.
A randomized controlled trial demonstrated significant reductions in fasting blood glucose and HbA1c levels in type 2 diabetic patients taking caper extract. Animal studies show promising anti-inflammatory effects in colitis models with decreased inflammatory cytokine levels. However, human clinical data remains limited, with most evidence coming from preclinical research. Larger, longer-term human studies are needed to confirm therapeutic potential.
Caper supplements are generally well-tolerated with minimal reported side effects in clinical studies. Individuals taking diabetes medications should monitor blood glucose closely due to potential additive glucose-lowering effects. No significant drug interactions have been documented, though caution is advised with anticoagulant medications due to flavonoid content. Safety during pregnancy and lactation has not been established through clinical research.
