Merged from 2 sources — review for redundancy.
Secondary plant metabolites (phytochemicals or secondary compounds) are bioactive plant compounds not directly involved in primary metabolism (growth, development, reproduction) but serving defensive, signaling, or ecological functions. Major classes include Polyphenols (flavonoids, phenolic acids), terpenoids (carotenoids, monoterpenes), alkaloids (caffeine, morphine), and glucosinolates (sulforaphane precursors). In humans, these compounds act as hormetic stressors and nutrient bioavailability enhancers—critical for optimal health but absent from isolated supplements.
Think of vitamins and minerals as raw building materials delivered to a construction site—pallets of bricks, steel beams, cement bags. Secondary plant metabolites are the entire construction crew: the forklift operators who unload the truck, the scaffolding that lets workers reach high places, the cranes that hoist materials to the right floor, and the site manager who coordinates everything.
Without the crew, the materials just sit in the parking lot. You can order more bricks (take more supplements), but they still won't get incorporated into the building. The Polyphenols in an orange don't just accompany vitamin C—they actively escort it across the gut barrier via specific transporters. The terpenoids in broccoli don't just sit alongside Zinc—they activate the cellular machinery (Nrf2 pathways) that tells cells to actually USE the zinc for antioxidant enzyme production.
This is why retest blood work after months of isolated vitamin/mineral supplementation often shows persistent deficiency: you've been delivering pallets of materials to a site with no workers. The "construction crew" compounds evolved together with nutrients in whole foods over millions of years—separating them is like expecting a building to construct itself.
Secondary plant metabolites exert their effects through multiple interconnected pathways:
Hormetic Stress Activation:
Plant defensive compounds → mild cellular oxidative stress → Nrf2 dissociation from Keap1 → Nrf2 nuclear translocation → binding to ARE (antioxidant response elements) → upregulation of:
- Phase II detoxification enzymes (GST, NQO1, GCLM)
- Antioxidant enzymes (SOD, catalase, glutathione peroxidase)
- Heat shock proteins
- Mitochondrial biogenesis (via PGC-1alpha)
Nutrient Bioavailability Enhancement:
- Transporter upregulation: Quercetin increases DMT1 expression → enhanced iron absorption; hesperidin increases SVCT1 → enhanced vitamin C uptake
- Mineral chelation: Catechins form bioavailable complexes with Zinc, Magnesium, preventing precipitation
- Enzyme modulation: Piperine (black pepper) inhibits glucuronidation → increased curcumin bioavailability by 2000%
- Bile acid signaling: Polyphenols activate FXR and TGR5 → enhanced fat-soluble vitamin absorption
Microbiome Interaction:
Secondary metabolites → selective prebiotic effects → increased Akkermansia-muciniphila, Faecalibacterium prausnitzii → enhanced SCFA production → improved gut barrier → reduced systemic inflammation → better nutrient utilization
Epigenetic Modulation:
Sulforaphane → HDAC inhibition → chromatin remodeling → altered gene expression for nutrient metabolism enzymes
graph TD
A[Secondary Plant Metabolites] --> B[Mild Oxidative Stress]
A --> C[Nutrient Transporter Binding]
A --> D[Microbiome Modulation]
B --> E[Nrf2 Activation]
E --> F[ARE Gene Transcription]
F --> G["↑ Antioxidant Enzymes"]
F --> H["↑ Phase II Detox"]
F --> I["↑ Mitochondrial Biogenesis"]
C --> J["↑ DMT1 Iron Transport"]
C --> K["↑ SVCT1 Vitamin C"]
C --> L[Mineral Chelation]
D --> M["↑ SCFA Production"]
M --> N["↑ Gut Barrier Function"]
N --> O["↓ Systemic Inflammation"]
O --> P[Improved Nutrient Utilization]
L --> P
K --> P
J --> P
I --> P
Specific Examples:
- Quercetin: Inhibits COMT → increased catecholamine half-life; inhibits xanthine oxidase → reduced uric acid; increases GLUT4 translocation → enhanced glucose uptake (requires Zinc as cofactor)
- Resveratrol: Activates SIRT3 → mitochondrial deacetylation → enhanced NAD+ recycling → improved B3 utilization
- Sulforaphane: Inhibits HDAC → upregulates NRF2 target genes including ferritin → improved iron storage and recycling
- EGCG: Inhibits folate polyglutamation → paradoxically increases bioavailable folate in high-dose scenarios; complexes with iron (both inhibitory and protective)
The Supplement Paradox:
Module 5's central clinical pearl: patients take high-dose isolated vitamins/minerals for months, retest shows persistent deficiency. Root cause: absence of secondary plant metabolites. Isolated ascorbic acid has ~50% lower bioavailability than vitamin C from citrus (which includes hesperidin, naringin). Isolated Zinc sulfate has 30-40% absorption; zinc from pumpkin seeds (with phytates paradoxically acting as slow-release carriers plus Polyphenols) achieves 60-70% utilization.
Metamodel Integration:
- Selfish Immune System: Polyphenols modulate immune cell glucose utilization—resveratrol shifts macrophages from M1 (glycolytic) to M2 (oxidative) phenotype, reducing metabolic competition between immune and muscle tissue
- Evolutionary Mismatch: Humans co-evolved with ~5,000-10,000 different secondary metabolites daily (hunter-gatherer diet); modern refined diets provide <500. This deprivation explains why isolated nutrient repletion fails—the cellular machinery expects the full molecular symphony
- Hormesis: Secondary metabolites are the original hormetic stressors—plants evolved them as toxins, we evolved to use them as signaling molecules (xenohormesis)
Clinical Thresholds:
- Minimum effective polyphenol intake: 500-1,000 mg/day (measured as gallic acid equivalents)
- Therapeutic doses for bioavailability enhancement: quercetin 500-1,000 mg with iron/Magnesium supplementation; piperine 5-20 mg with curcumin
- Nrf2 activation threshold: varies by compound but generally requires consistent daily exposure (sulforaphane 30-60 mg glucoraphanin equivalent)
Intervention Strategy:
- Never supplement isolated nutrients long-term without whole-food matrix or extracted secondary metabolites
- Combine mineral supplementation with specific enhancers: Zinc + quercetin; iron + vitamin C + Polyphenols; Magnesium + Vitamin B6 + green tea extract
- Prioritize dietary diversity: 30+ different plant foods weekly (each contributes unique secondary metabolite profile)
- Use therapeutic extracts strategically: standardized curcumin with piperine for inflammation; resveratrol for mitochondrial support; sulforaphane for detoxification
- Address gut dysbiosis: secondary metabolites require healthy microbiome for conversion to active forms (e.g., soy isoflavones → equol requires specific bacteria)
Wound Healing Application (Module 5):
The connective tissue slides demonstrate that Zinc supplementation (20-30 mg daily) for wound healing has limited efficacy without:
- Humans evolved consuming 5,000-10,000 different phytochemicals daily; modern diets provide <500
- Quercetin increases intestinal iron absorption by 50-67% via DMT1 upregulation
- Piperine enhances curcumin bioavailability by 2,000% through glucuronidation inhibition
- Secondary metabolites activate Nrf2 at concentrations 100-1,000× lower than direct oxidants
- Isolated vitamin C has 50% lower bioavailability than citrus-derived vitamin C with hesperidin
- Sulforaphane (from broccoli) increases glutathione synthesis 200-300% via GCLM upregulation
- Polyphenols constitute 1-2 g daily intake in Mediterranean diet vs. <200 mg in standard Western diet
- Resveratrol activates SIRT3 at 10-50 μM concentrations → enhanced NAD+ utilization
- EGCG forms complexes with iron preventing oxidative damage while maintaining bioavailability
- Secondary metabolites comprise ~200,000 known compounds across plant kingdom vs. ~20 essential vitamins/minerals
- Minimum therapeutic polyphenol intake: 500-1,000 mg/day (gallic acid equivalents)
- Glucosinolates (broccoli family) require myrosinase enzyme for conversion to active sulforaphane—destroyed by >60°C cooking
- Polyphenols — largest and most studied category of secondary plant metabolites with direct nutrient bioavailability effects
- Quercetin — exemplar flavonoid that enhances iron, Zinc, and Magnesium absorption via transporter upregulation
- Nrf2 — master transcription factor activated by hormetic stress from phytochemicals, coordinates antioxidant and detoxification responses
- Hormesis — fundamental principle explaining beneficial effects of mildly toxic plant compounds
- Microbiome — required for conversion of many secondary metabolites to bioactive forms (isoflavones, lignans, ellagitannins)
- SCFA — produced when gut microbiota ferment polyphenolic compounds, enhancing nutrient absorption
- Zinc — bioavailability dramatically enhanced by quercetin and other flavonoids; essential for Nrf2 pathway function
- Magnesium — absorption improved by polyphenol-mediated gut barrier enhancement and transporter regulation
- Vitamin C — always found with bioflavonoids in nature; synergistic effects on collagen synthesis and iron absorption
- Antioxidant — upregulated endogenously by phytochemical-induced Nrf2 activation rather than direct ROS scavenging
- Mitochondrial biogenesis — triggered by resveratrol, quercetin via PGC-1alpha and SIRT3 activation
- Gut barrier — strengthened by polyphenol-induced tight junction protein expression and microbiome modulation
- Inflammation — modulated by secondary metabolites through multiple pathways (NF-κB inhibition, NLRP3 regulation, SPM precursor provision)
- Wound healing — requires synergy between Zinc, vitamin C, and phytochemicals for optimal collagen synthesis and tissue repair
- Detoxification — Phase II enzyme upregulation via sulforaphane and other Nrf2 activators
- Iron — absorption enhanced 50-67% by vitamin C plus quercetin; storage improved by polyphenol-induced ferritin expression
- Evolutionary mismatch — modern refined diets lack phytochemical diversity present throughout human evolution
- Nutrient bioavailability — the core clinical issue—isolated supplements fail because they lack the phytochemical "crew"
- CYP450 — cytochrome P450 enzymes modulated by secondary metabolites affecting drug and nutrient metabolism
- Epigenetic modifications — HDAC inhibition by sulforaphane alters gene expression for nutrient metabolism enzymes
- Vitamin D receptor — expression upregulated by resveratrol and curcumin, improving vitamin D signaling
- Akkermansia-muciniphila — increased by polyphenol consumption, enhances gut barrier and metabolic health
- Glucose metabolism — improved by resveratrol (GLUT4 translocation), EGCG, and berberine through AMPK activation
Secondary plant metabolites are bioactive compounds produced by plants not directly involved in growth, development, or reproduction. They include Polyphenols, terpenoids, alkaloids, and flavonoids that evolved as plant defense mechanisms against herbivores, pathogens, and environmental stress. In humans, these compounds trigger Hormesis—low-dose stressors that activate adaptive cellular pathways including Nrf2 antioxidant defense, NF-κB modulation, and gut microbiome regulation, while simultaneously serving as essential cofactors for micronutrients absorption.
Imagine your body is a construction site trying to build walls (collagen, enzymes, cellular structures). You've ordered bricks (Vitamins, Minerals) and they arrive on trucks. But without the skilled foremen—the secondary plant metabolites—the bricks just pile up in the yard unused. The foremen don't build the walls themselves; they're the ones who show the workers where to place bricks, how to mix mortar properly, and when to reinforce weak spots.
When you take isolated vitamin supplements without eating colorful plants, it's like dumping bricks on-site without foremen—blood tests show the bricks arrived (high serum levels), but the walls aren't getting built (tissue deficiency persists). The polyphenols, flavonoids, and terpenoids are the foremen who activate the workers (enzymes), open the gates for delivery (enhance bioavailability), and even trigger the alarm system when invaders approach (mild stress response that strengthens defenses). This is why a zinc supplement alone often fails, but zinc from oysters with their full phytochemical package succeeds—you get both bricks and foremen.
Secondary plant metabolites exert effects through multiple interconnected pathways:
Nrf2 Activation Pathway:
Polyphenols (curcumin, sulforaphane, resveratrol) -> electrophilic stress -> Keap1 oxidation -> Nrf2 release from cytoplasm -> nuclear translocation -> ARE (Antioxidant Response Element) binding -> transcription of: NQO1, HO-1, GST, glutathione synthesis enzymes, SOD, catalase -> enhanced antioxidant capacity and phase II Detoxification
NF-κB Modulation:
Secondary metabolites (EGCG, quercetin) -> inhibit IκB kinase -> prevent IκB degradation -> NF-κB remains sequestered in cytoplasm -> reduced transcription of: TNF-α, IL-1β, IL-6, COX-2, iNOS -> anti-inflammatory effect. Some compounds also acetylate p65 subunit directly, reducing DNA binding affinity.
Enzyme Inhibition:
- COX-2 inhibition: flavonoids compete at arachidonic acid binding site -> reduced PGE2 and inflammatory Prostaglandins
- LOX inhibition: polyphenols block 5-LOX and 12-LOX -> reduced Leukotriene B4 and inflammatory leukotrienes
- α-glucosidase/α-amylase inhibition: tannins delay carbohydrate breakdown -> reduced postprandial glucose spike
Microbiome Modulation:
Most polyphenols are poorly absorbed in small intestine (5-10% bioavailability) -> reach colon intact -> serve as selective prebiotics -> Akkermansia-muciniphila, Lactobacillus, Bifidobacteria metabolize them into bioactive metabolites (urolithins from ellagitannins, equol from daidzein, 3,4-dihydroxyphenylacetic acid from quercetin) -> these metabolites have superior absorption and activity compared to parent compounds -> also produce SCFAs alongside fiber fermentation
Metal Chelation:
Catechol and gallate groups form coordination complexes with iron, copper, zinc -> enhance mineral solubility at intestinal pH -> facilitate absorption via DMT1 and other transporters -> also sequester excess metals preventing Fenton reaction (Fe²⁺ + H₂O₂ -> Fe³⁺ + OH• + OH⁻)
graph TD
A[Secondary Plant Metabolites ingested] --> B["Small intestine: 5-10% absorbed"]
A --> C["Colon: 90-95% reach intact"]
B --> D["Direct effects: Nrf2 activation"]
B --> E["Direct effects: NF-κB inhibition"]
B --> F["Enzyme inhibition: COX-2, LOX"]
C --> G[Microbiome fermentation]
G --> H[Urolithins, equol, other metabolites]
G --> I[SCFA production enhanced]
H --> J[Systemic absorption of metabolites]
J --> K[Anti-inflammatory signaling]
D --> L[Increased antioxidant enzymes]
E --> L
F --> L
K --> L
I --> M[Gut barrier strengthening]
L --> N[Enhanced nutrient bioavailability]
M --> N
N --> O[Tissue-level vitamin/mineral utilization]
Hormetic Dose-Response:
Low doses (typical dietary intake: 200-500 mg polyphenols/day) -> beneficial adaptive stress -> upregulation protective pathways
High doses (isolated supplements >2000 mg/day) -> oxidative stress exceeds adaptive capacity -> potential pro-oxidant effects, DNA damage, hepatotoxicity (documented with green tea extract >800 mg EGCG/day)
This concept is foundational to understanding why nutrient repletion protocols fail without whole-food context—a cornerstone Pruimboom teaching. Patients present with documented deficiencies (ferritin <30 ng/mL, serum zinc <70 μg/dL, vitamin D <30 ng/mL), supplement for months, retest still deficient despite adequate intake. The missing link: secondary plant metabolites.
Evolutionary Medicine Perspective:
Humans co-evolved with plants consuming 100+ different plant species seasonally, exposing us to thousands of phytochemicals. Universal human mutations like loss of Vitamin C synthesis (GULO mutation) and uricase mutation occurred because abundant dietary polyphenols provided redundant antioxidant protection—we outsourced these functions. Modern refined diets eliminate this evolutionary partnership, creating a Mismatch Disease scenario where isolated nutrients cannot function without their ancestral cofactors.
Clinical Applications by System:
Immune System:
- Chronic low-grade inflammation (CRP 3-10 mg/L): polyphenol-rich extracts (curcumin 500-1000 mg, resveratrol 150-300 mg) downregulate NF-κB, reduce inflammatory cytokine production
- Autoimmunity: EGCG 300-600 mg modulates T cell differentiation, reduces Th1/Th17 dominance in conditions like rheumatoid arthritis
- Post-infection resolution: specialized pro-resolving mediators require adequate omega-3 levels, but conversion of EPA/DHA to Resolvins enhanced by polyphenol-mediated enzyme activity
Metabolic System:
- Insulin resistance: berberine (900-1500 mg/day) activates AMPK similar to metformin, improves GLUT4 translocation
- NAFLD/NASH: silymarin (milk thistle) 420-600 mg protects hepatocytes via Nrf2 activation, reduces ALT/AST
- Type 2 Diabetes: cinnamon extract standardized to polyphenols improves HbA1c by 0.5-1.0% through enhanced insulin signaling
Gut Health:
Connective Tissue/Wound Healing:
As noted in Module 5 connective tissue walkthrough, Zinc 20-30 mg daily is essential for wound healing, but absorption is profoundly enhanced by flavonoids that chelate zinc into soluble complexes. Patients taking zinc gluconate alone show minimal tissue improvement; same dose with quercetin-rich foods (onions, apples, berries) demonstrates clinical healing response within 2-3 weeks.
Intervention Protocol (5+2 Metamodel Integration):
-
Nutrition (Metamodel 1): Prescribe "eating the rainbow"—minimum 5 different colored vegetables daily, each color indicates different phytochemical profiles (red = lycopene/anthocyanins, orange = carotenoids, green = chlorophyll/sulforaphane, purple = anthocyanins, white/tan = allicin/quercetin)
-
Supplement Strategy: When supplementing vitamins/minerals, always combine with polyphenol-rich extract or recommend taking with meals containing abundant plants. For example: iron supplementation with vitamin C (ascorbic acid) PLUS quercetin 250 mg, or calcium/magnesium with Vitamin K2 in context of dark leafy greens
-
Microbiome Support (Metamodel 2): Recognize most polyphenol benefit comes from microbial transformation—protocols must include prebiotic fiber alongside polyphenols to feed transforming bacteria
-
Dosing Considerations: Respect hormetic curve—more is not better. Therapeutic doses: curcumin 500-2000 mg, resveratrol 150-500 mg, EGCG 200-600 mg, quercetin 500-1000 mg. Avoid mega-doses that exceed adaptive capacity.
Exam-Relevant Clinical Pearl:
When patients report "supplements don't work for me," first question is not "what dose?" but "are you eating colorful plants with every meal?" This single diagnostic question reveals whether they understand the cofactor principle that separates functional from failing protocols.
- Over 200,000 secondary metabolites identified across plant kingdom; humans evolved consuming 100+ plant species providing thousands of phytochemicals
- Only 5-10% of most polyphenols absorbed in small intestine; 90-95% reach colon where microbiome transforms them into more bioavailable metabolites
- Colorful pigmentation signals high secondary metabolite content: anthocyanins (purple/red), carotenoids (orange/yellow), chlorophyll (green), betalains (deep red)
- Hormetic dose-response: dietary levels (200-500 mg total polyphenols/day) beneficial; isolated supplement mega-doses (>2000 mg/day) can be pro-oxidant and hepatotoxic
- Curcumin has 1% oral bioavailability alone but increases to 20-fold with piperine (black pepper alkaloid) or phosphatidylcholine complexing
- EGCG from green tea inhibits COMT enzyme that degrades catecholamines—explains why green tea provides sustained calm energy vs coffee crash
- Quercetin is most abundant dietary flavonoid (avg intake 10-100 mg/day from onions, apples, berries) with half-life of 11-28 hours
- Resveratrol activates sirtuins (SIRT1) and AMPK mimicking caloric restriction benefits at 150-300 mg/day
- Food processing destroys 50-90% of secondary metabolites: white flour vs whole wheat, refined oils vs cold-pressed, canned vs fresh
- Pruimboom principle: "You cannot absorb micronutrients without secondary plant metabolites"—mechanism involves enhanced transporter activity, chelation increasing solubility, and reduced oxidative damage to absorptive epithelium
- Major polyphenol classes: flavonoids (6 subclasses including flavonols, flavanols, anthocyanins), phenolic acids (caffeic, ferulic), stilbenes (resveratrol), lignans (flaxseed)
- Nrf2 activation by sulforaphane (broccoli sprouts) increases glutathione synthesis enzymes within 3-6 hours, peak effect 48-72 hours
- Metal chelation by polyphenols: catechol groups form coordination complexes with Fe²⁺, Cu²⁺, Zn²⁺ at pH 6-7, enhancing absorption while preventing Fenton oxidative damage
- Microbiome diversity correlates with dietary polyphenol diversity more strongly than fiber intake alone—polyphenols are selective prebiotics
- Polyphenols — largest and most studied class of secondary plant metabolites with thousands of identified compounds
- Flavonoids — polyphenol subclass including quercetin, EGCG, anthocyanins with specific anti-inflammatory and antioxidant mechanisms
- Curcumin — turmeric polyphenol that inhibits NF-κB, activates Nrf2, modulates cytokine production; bioavailability enhanced 2000% with piperine
- Resveratrol — stilbene polyphenol from grapes activating SIRT1 and mimicking caloric restriction benefits
- EGCG — green tea catechin inhibiting COMT, COX-2, and activating AMPK with metabolic benefits
- Quercetin — most abundant dietary flavonoid strengthening tight junctions, chelating metals, inhibiting viral replication
- Rutin — glycosylated quercetin that inhibits COMT preventing dopamine degradation
- Hormesis — fundamental mechanism whereby low-dose stressors (including phytochemicals) trigger beneficial adaptive responses
- Nrf2 — master transcription factor activated by electrophilic phytochemicals coordinating 200+ antioxidant/detox genes
- NF-κB — inflammatory transcription factor inhibited by most polyphenols preventing cytokine storm
- Antioxidant — many secondary metabolites directly scavenge ROS while also upregulating endogenous antioxidant enzymes
- Gut microbiome — transforms poorly absorbed polyphenols into bioactive metabolites with superior absorption and activity
- Akkermansia-muciniphila — keystone species selectively fed by polyphenols, produces mucus-strengthening compounds
- Bifidobacteria — polyphenol-metabolizing bacteria producing anti-inflammatory metabolites and SCFAs
- Faecalibacterium prausnitzii — butyrate producer enhanced by polyphenol-rich diets, inversely correlated with inflammation
- SCFAs — short-chain fatty acids co-produced when microbiome ferments both fiber and polyphenols together
- Bioavailability — secondary metabolites dramatically enhance mineral/vitamin absorption via chelation, transporter upregulation, barrier protection
- Vitamins — absorption and tissue utilization profoundly dependent on phytochemical cofactors
- Minerals — solubility and transport across gut epithelium enhanced by polyphenol chelation
- Zinc — absorption increased 2-3 fold when taken with quercetin or other flavonoids that form soluble complexes
- Magnesium — flavonoid complexes increase bioavailability and reduce GI side effects
- Iron — polyphenols have biphasic effect: low doses enhance absorption via chelation, high doses (tea with meals) inhibit via tight binding
- COX-2 — enzyme inhibited by multiple phytochemicals reducing prostaglandin synthesis and inflammation
- 5-LOX — lipoxygenase enzyme blocked by polyphenols preventing leukotriene formation
- Chronic low-grade inflammation — secondary metabolites are primary dietary modulators downregulating inflammatory pathways
- Detoxification — phase II conjugation enzymes (GST, UGT, SULT) upregulated by Nrf2-activating phytochemicals
- Insulin resistance — berberine, cinnamon polyphenols activate AMPK improving glucose uptake independent of insulin
- NAFLD — silymarin and other hepatoprotective polyphenols reduce steatosis via Nrf2 activation and lipid metabolism modulation
- Type 2 Diabetes — multiple phytochemicals improve glycemic control through enzyme inhibition, insulin sensitization, inflammation reduction
- Leaky gut — quercetin and other flavonoids strengthen tight junction proteins preventing increased intestinal permeability
- Zonulin — polyphenols reduce zonulin release preventing tight junction disassembly
- Dysbiosis — diverse polyphenol intake reshapes microbiome favoring beneficial over pathogenic species
- IBD — curcumin and other anti-inflammatory phytochemicals reduce mucosal inflammation and extend remission
- Autoimmunity — EGCG modulates T cell differentiation reducing autoimmune reactivity
- Wound healing — flavonoids enhance collagen synthesis by improving zinc/vitamin C function and reducing oxidative damage
- Evolutionary medicine — human dependence on phytochemicals reflects co-evolution with plant-rich diets; their absence creates mismatch disease
- Mismatch Disease — modern refined diets lacking secondary metabolites create nutrient malabsorption despite adequate intake
- AMPK — activated by resveratrol, berberine, EGCG mimicking exercise and fasting metabolic benefits
- mTORC1 — inhibited by polyphenols promoting autophagy and longevity pathways
- Autophagy — enhanced by polyphenol-mediated AMPK activation and mTOR inhibition supporting cellular cleanup
- Mitohormesis — mild mitochondrial stress from phytochemicals triggers adaptive increase in mitochondrial biogenesis
- Oxidative Stress — biphasic effect: low-dose polyphenols reduce oxidative damage; high doses can be pro-oxidant
- AGEs — advanced glycation end-products formation inhibited by polyphenol antioxidants protecting against diabetic complications