Amaranth Leaf (Amaranthus spp.)

Amaranth leaf (Amaranthus spp.) is a nutrient-dense dark leafy green containing bioactive compounds including rutin, quercetin, and betalains that exert antioxidant and neuroprotective effects. These polyphenols modulate oxidative stress pathways by scavenging free radicals and reducing lipid peroxidation markers such as malondialdehyde in neural tissue.

Origin & History

Amaranth leaf derives from plants of the genus Amaranthus spp., including cultivated varieties like A. cruentus, A. hybridus, A. dubius, and A. retroflexus, native to tropical and subtropical regions worldwide. The leaves are harvested fresh and processed into extracts using water or organic solvents, classified as a USDA nutrient-dense food due to high levels of vitamins, minerals, and antioxidants.

Historical & Cultural Context

Sources do not detail specific historical traditional medicine systems or durations for amaranth leaf use. It is noted as a nutrient-dense food with recent research interest in health benefits like antidiabetic potential, with modern processing into functional food powders.

Health Benefits

• Cognitive support: Aqueous leaf extract (200-400 mg/kg) significantly improved memory in mouse models, comparable to donepezil (preliminary evidence)
• Antioxidant protection: Reduced brain malondialdehyde levels and oxidative stress markers in preclinical studies (animal evidence only)
• Antifungal activity: In vitro studies showed 66-80% inhibition against R. solani at 10-15 mg/mL (laboratory evidence)
• Potential anticancer effects: Inhibited tumor cell growth by 43-45% in vitro (cell culture evidence only)
• Nitric oxide modulation: Single oral dose elevated plasma nitrate/nitrite for 8 hours in humans (limited human data)

How It Works

Quercetin and rutin in amaranth leaf inhibit pro-oxidant enzymes and upregulate endogenous antioxidant defenses, reducing malondialdehyde accumulation and protecting neuronal membranes from lipid peroxidation. Rutin has been shown to modulate acetylcholinesterase activity, potentially preserving cholinergic neurotransmission relevant to memory consolidation. Betalains and other phenolic compounds additionally exhibit direct free-radical scavenging via hydrogen atom transfer and single-electron transfer mechanisms.

Scientific Research

No human clinical trials, RCTs, or meta-analyses on amaranth leaf were identified; evidence is limited to preclinical animal and in vitro studies. A single human pharmacokinetic study showed nitrate/nitrite elevation after oral dosing, while mouse studies demonstrated cognitive enhancement and antioxidant effects at 200-400 mg/kg body weight.

Clinical Summary

Current evidence for amaranth leaf is largely preclinical, with mouse model studies using aqueous leaf extracts at 200–400 mg/kg demonstrating significant memory improvement comparable to the cholinesterase inhibitor donepezil. Oxidative stress markers, particularly brain malondialdehyde levels, were significantly reduced in these animal studies, suggesting neuroprotective potential. Antifungal activity has been documented in in vitro assays against common pathogenic fungi, though no robust human randomized controlled trials have confirmed these effects at relevant oral doses. The overall evidence quality is preliminary, and extrapolation to human therapeutic use requires further clinical investigation.

Nutritional Profile

Amaranth leaves are nutritionally dense per 100g fresh weight: Protein: 2.5-3.5g (high biological value with essential amino acids including lysine ~0.7g, which is limiting in many plant proteins); Total carbohydrates: 4-6g; Dietary fiber: 2-3g; Fat: 0.2-0.5g. Key vitamins: Vitamin C: 40-80mg (44-89% DV, though heat-labile and reduced significantly by cooking); Vitamin A (as beta-carotene precursor): 1500-3000 µg RAE equivalent (substantial contributor to daily needs); Folate (B9): 85-120µg; Riboflavin (B2): 0.16mg; Thiamine (B1): 0.05mg. Key minerals: Calcium: 200-410mg per 100g (notably high for a leafy vegetable, though bioavailability is moderately reduced by oxalate content ~700-1200mg/100g which binds calcium); Iron: 3-4mg (non-heme, bioavailability enhanced by co-consumption with vitamin C sources); Magnesium: 55-70mg; Potassium: 400-600mg; Phosphorus: 50-75mg; Zinc: 0.9mg. Bioactive compounds: Betalains (betacyanins and betaxanthins) in pigmented varieties; polyphenols including rutin, quercetin, and kaempferol derivatives (~200-400mg total phenolics per 100g dry weight); amaranthine pigment in red varieties; squalene in minor amounts. Carotenoids: lutein and zeaxanthin present (~1200-2000µg/100g). Bioavailability notes: Oxalates and phytates (~400-800mg/100g) reduce mineral absorption; blanching or boiling reduces oxalate content by 30-60% and improves net mineral bioavailability; protein digestibility corrected amino acid score (PDCAAS) estimated at 0.75-0.85, superior to many other leafy greens.

Preparation & Dosage

No clinically studied dosages in humans are available. Mouse studies used aqueous leaf extract at 200-400 mg/kg body weight daily for cognitive effects, with 300 mg/kg showing peak benefits. In vitro antifungal studies used 10-15 mg/mL concentrations. Consult a healthcare provider before starting any new supplement.

Synergy & Pairings

Donepezil alternatives, Antioxidant complexes, Nitric oxide precursors, Polyphenol blends, Dark leafy greens

Safety & Interactions

Amaranth leaf consumed as a food is generally recognized as safe; however, concentrated extracts have not been evaluated in large-scale human safety trials. Individuals taking anticoagulants such as warfarin should exercise caution, as quercetin and rutin may have mild antiplatelet and anticoagulant properties that could potentiate bleeding risk. Amaranth contains moderate oxalate levels, posing a theoretical risk for kidney stone formation in predisposed individuals with high chronic intake. Pregnant and breastfeeding women should limit use to culinary quantities, as the safety of concentrated extracts in these populations has not been established.