Amaranthus cruentus (Red Amaranth)

Amaranthus cruentus, or red amaranth, is a dark leafy green rich in betacyanins (40.42 mg/100g dry weight) and phenolic compounds that neutralize free radicals through electron donation and metal ion chelation. Its antioxidant activity, measured at IC₅₀ values of 56–423 µg/mL, positions it as a functional food candidate, though human clinical evidence remains limited.

Origin & History

Amaranthus cruentus (red amaranth) is a leafy vegetable and grain crop native to Central and South America, belonging to the Amaranthaceae family. The plant is harvested for both its nutrient-dense leaves and seeds, which are processed into fresh plant material, dried powder, and phytochemical extracts. Red amaranth is classified as a USDA nutrient-dense food due to its high concentration of bioactive compounds including betacyanins, flavonoids, and phenolic compounds.

Historical & Cultural Context

Traditional use information for red amaranth in historical medicine systems was not included in the provided research. The available studies focus exclusively on modern phytochemical analysis and agricultural applications.

Health Benefits

• Antioxidant activity: Contains phenolic compounds with free-radical scavenging activity (IC₅₀ 56-423 µg/mL) and iron-reducing power of 2.26-2.56 mmol ascorbic acid equivalent/gram (preliminary evidence from in-vitro studies)
• Rich phytochemical profile: Provides betacyanins (40.42 mg/100g dry weight), flavonoids (0.37-7.06 mg/100mg extract), and tannins (2.83-10.17 mg/100mg extract) (compositional analysis only)
• Nutrient density: Classified as USDA nutrient-dense food with high concentrations of calcium, potassium, and magnesium (based on compositional data)
• Diverse bioactive compounds: Contains polyphenols, steroids, terpenoids, saponins, and betalains extracted optimally with hydroacetonic solvents (phytochemical characterization study)
• Potential metabolic support: In animal models, demonstrates ability to modulate fermentation and reduce methane production (preliminary animal evidence only)

How It Works

Betacyanins in Amaranthus cruentus donate hydrogen atoms to reactive oxygen species, interrupting lipid peroxidation chain reactions and reducing ferric ions (Fe³⁺) to ferrous ions (Fe²⁺) at a rate of 2.26–2.56 mmol ascorbic acid equivalent per gram, reflecting significant iron-reducing capacity. Phenolic compounds including rutin and quercetin derivatives inhibit pro-inflammatory enzymes such as cyclooxygenase (COX) and lipoxygenase (LOX) by competing at their active sites. Additionally, betacyanins may upregulate endogenous antioxidant enzymes including superoxide dismutase (SOD) and catalase via Nrf2 pathway activation, though this mechanism is currently supported only by in-vitro and animal data.

Scientific Research

The current research on red amaranth consists primarily of phytochemical characterization studies and animal feed applications. No human clinical trials, randomized controlled trials, or meta-analyses were available in the provided research. The existing studies focus on compositional analysis of bioactive compounds and antioxidant activity through in-vitro methods.

Clinical Summary

Current evidence for Amaranthus cruentus is primarily derived from in-vitro assays and preliminary phytochemical analyses, with no large-scale randomized controlled trials in humans published to date. In-vitro studies using DPPH and FRAP assays have quantified free-radical scavenging at IC₅₀ values ranging from 56 to 423 µg/mL depending on extraction solvent and plant part tested. Animal studies have suggested anti-inflammatory and hepatoprotective effects at doses of 200–400 mg/kg body weight, but direct extrapolation to human dosing remains speculative. The overall evidence quality is low-to-preliminary, and health claims beyond nutritional value require validation through well-designed human trials.

Nutritional Profile

Red Amaranth (Amaranthus cruentus) leaves and seeds provide a dense nutritional profile. Macronutrients (per 100g fresh leaves): protein 2.5–3.5g (notably high for a leafy vegetable, containing essential amino acids including lysine at ~5.3g/100g protein — superior to most cereals); carbohydrates 4.0–5.5g; dietary fiber 2.0–3.2g; fat 0.3–0.5g; moisture 85–90g. Seeds are more calorie-dense: protein 13–18g/100g dry weight, fat 6–8g (rich in unsaturated fatty acids, ~77% linoleic and oleic acids), starch 50–60g, and squalene (~5–8% of seed oil, a bioactive triterpene). Micronutrients (per 100g fresh leaves): calcium 267–415mg (among the highest of leafy vegetables, though bioavailability is reduced ~50–70% due to oxalic acid content of 700–870mg/100g forming insoluble calcium oxalate); iron 3.0–4.6mg (non-heme; absorption enhanced by co-consumed vitamin C); magnesium 55–75mg; potassium 340–480mg; phosphorus 50–70mg; zinc 0.9–1.2mg. Vitamins: vitamin C 43–80mg/100g fresh weight (heat-labile; significantly reduced by boiling); beta-carotene (provitamin A) 1.5–4.0mg/100g (fat-soluble; bioavailability improved with dietary fat); folate 85–120µg/100g; vitamin K approximately 300–400µg/100g (clinically relevant for anticoagulant drug interactions). Bioactive compounds: betacyanins (red pigments, primarily amaranthine) at 40.42mg/100g dry weight contributing antioxidant capacity; flavonoids 0.37–7.06mg/100mg extract (including rutin and quercetin derivatives); tannins 2.83–10.17mg/100mg extract (may reduce protein and mineral bioavailability at high intakes); phenolic acids including gallic and caffeic acid derivatives. Antinutrients: oxalates (~870mg/100g fresh), phytates (0.4–0.9g/100g dry seed), and tannins collectively reduce mineral bioavailability; blanching or boiling reduces oxalate content by 30–60% and phytates by ~40%, improving net mineral absorption.

Preparation & Dosage

No clinically studied dosage ranges for human consumption are available from the current research. The studies provided only address phytochemical extraction methods and animal feed supplementation levels, which are not applicable to human dosing recommendations. Consult a healthcare provider before starting any new supplement.

Synergy & Pairings

Other dark leafy greens, vitamin C sources, iron-rich foods, antioxidant-rich berries, quercetin supplements

Safety & Interactions

Amaranthus cruentus is generally recognized as safe when consumed as a food, but concentrated extracts have not been evaluated in formal human toxicity trials. Its notable oxalate content (comparable to other amaranth species) may increase kidney stone risk in individuals with calcium-oxalate nephrolithiasis or impaired renal function. The plant's iron-reducing compounds may theoretically interact with iron-chelation therapies or alter the absorption of co-administered minerals such as zinc and calcium. Pregnant and breastfeeding women should limit use to culinary amounts, as pharmacological doses lack safety data in these populations.