# Synephrine (Protoalkaloid)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/synephrine
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-19
**Evidence Score:** 8 / 10
**Category:** Compound
**Also Known As:** p-synephrine, 4-[1-hydroxy-2-(methylamino)ethyl]phenol, oxedrine, sympatol, zhi shi, bitter orange alkaloid, neo-synephrine

## Overview

Synephrine is a protoalkaloid derived from bitter orange that acts as a selective β1-adrenergic receptor agonist. It increases [metabolic rate](/ingredients/condition/weight-management) by 129-183 kcal daily and enhances fat oxidation through stimulation of lipolytic pathways.

## Health Benefits

• Increases resting [metabolic rate](/ingredients/condition/weight-management) (RMR) by 129-183 kcal - demonstrated in double-blind RCT (PMID: 21537493)
• Enhances fat oxidation during exercise via adrenergic stimulation - mechanistic evidence from β1-receptor agonist activity
• Reduces inflammation through inhibition of p38 MAPK and NF-κB pathways - shown to decrease TNF-α and IL-6 in cellular studies
• No significant [cardiovascular](/ingredients/condition/heart-health) effects at 49mg dose - confirmed in crossover RCT with 18 subjects (PMID: 26948284)
• Promotes glucose uptake and shifts microglia to [anti-inflammatory](/ingredients/condition/inflammation) M2 phenotype - preliminary in-vitro evidence

## Mechanism of Action

Synephrine selectively binds to β1-adrenergic receptors, activating adenylyl cyclase and increasing cAMP levels. This stimulates hormone-sensitive lipase for enhanced lipolysis and increases [thermogenesis](/ingredients/condition/weight-management) through uncoupling protein activation. It also inhibits [inflammatory pathway](/ingredients/condition/inflammation)s by suppressing p38 MAPK and NF-κB signaling cascades.

## Clinical Summary

A double-blind randomized controlled trial demonstrated synephrine increases resting [metabolic rate](/ingredients/condition/weight-management) by 129-183 kcal in healthy adults. Multiple studies show enhanced fat oxidation rates during exercise through adrenergic stimulation mechanisms. [Anti-inflammatory](/ingredients/condition/inflammation) effects have been documented through p38 MAPK and NF-κB pathway inhibition studies. However, long-term weight loss efficacy requires more extensive clinical investigation.

## Nutritional Profile

Synephrine is a protoalkaloid (phenethylamine derivative) with molecular formula C9H13NO2 and molecular weight 167.21 g/mol. It is not a macronutrient or micronutrient source but a pharmacologically active bioactive compound. Naturally occurring concentrations: bitter orange (Citrus aurantium) peel contains 0.02–0.07% synephrine by dry weight (~200–700 mg/kg); immature fruit (zhi shi) contains higher concentrations of 1–6% by dry weight in some extracts. Standardized commercial extracts are typically standardized to 6% or 10–30% synephrine content. Primary bioactive form: p-synephrine (para-synephrine) is the predominant naturally occurring isomer; m-synephrine (meta-synephrine, oxedrine) is the pharmacologically distinct synthetic form. Oral bioavailability: approximately 30–40% for p-synephrine due to first-pass hepatic [metabolism](/ingredients/condition/weight-management); peak plasma concentration (Tmax) reached within 1–2 hours post-ingestion. Typical studied doses range from 50–100 mg p-synephrine per serving in clinical trials (e.g., 50 mg yielding RMR increase of 129–183 kcal per PMID: 21537493). No meaningful macronutrient (carbohydrate, fat, protein), fiber, vitamin, or mineral content attributable to synephrine itself as an isolated compound. Metabolized primarily via monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) pathways; co-administration with MAO inhibitors significantly alters metabolism and bioavailability.

## Dosage & Preparation

Clinically studied doses range from 30-50mg p-synephrine acutely, or 36-132mg/day for 14-56 days. Standardized bitter orange extracts containing 4-6% p-synephrine (1g extract providing 30-50mg) have been used in RCTs. Isolated p-synephrine at 50mg alone raised RMR without [cardiovascular](/ingredients/condition/heart-health) changes. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Synephrine is generally well-tolerated at doses up to 50mg daily, with mild side effects including increased heart rate and [blood pressure](/ingredients/condition/heart-health). It may interact with MAO inhibitors and stimulant medications, potentially causing hypertensive episodes. Individuals with cardiovascular conditions, hypertension, or taking heart medications should avoid synephrine. Safety during pregnancy and lactation has not been established, so use is not recommended.

## Scientific Research

A 2022 meta-analysis of placebo-controlled trials found p-synephrine tends to raise [blood pressure](/ingredients/condition/heart-health) and heart rate without facilitating weight loss. Key RCTs include an 18-subject crossover trial (PMID: 26948284) showing no cardiovascular effects at 49mg, and a double-blind RCT (PMID: 21537493) demonstrating 50mg p-synephrine increased RMR by up to 183 kcal. A review of ~20 studies involving ~360 subjects confirmed safety at typical doses, though longer trials up to 56 days showed increased RMR without weight loss.

## Historical & Cultural Context

In Traditional Chinese Medicine, Citrus aurantium (Zhi Shi) has been used for over 1,000 years to promote [digestion](/ingredients/condition/gut-health), relieve abdominal distension, and treat qi stagnation. European herbalism has historically used synephrine-containing extracts for weight control and respiratory issues, though modern clinical focus on isolated p-synephrine is relatively recent.

## Synergistic Combinations

Naringin, Hesperidin, Green Tea Extract (EGCG), L-Carnitine, Chromium

## Frequently Asked Questions

### How much does synephrine increase metabolism?

Clinical studies show synephrine increases resting metabolic rate by 129-183 calories per day. This metabolic boost occurs within 2-3 hours of supplementation and can last up to 6 hours.

### What is the effective dosage of synephrine?

The clinically effective dose ranges from 10-50mg daily, typically taken 30 minutes before meals. Most studies use 20-30mg doses to balance efficacy with minimal side effects.

### Does synephrine cause the same side effects as ephedrine?

Synephrine has a better safety profile than ephedrine due to selective β1-receptor activity rather than broad adrenergic stimulation. It causes less cardiovascular stress and fewer central nervous system side effects.

### Can synephrine be combined with caffeine?

Synephrine can be safely combined with moderate caffeine doses (100-200mg) and may enhance fat-burning effects. However, this combination may increase heart rate and should be monitored in sensitive individuals.

### How long does synephrine stay active in the body?

Synephrine has a half-life of approximately 2-3 hours with peak blood levels occurring 1-2 hours after oral administration. Metabolic effects typically last 4-6 hours following supplementation.

### What natural food sources contain synephrine?

Synephrine is naturally found in citrus fruits, particularly in bitter orange (Citrus aurantium) peel and immature citrus varieties. While whole citrus fruits contain synephrine, the concentration is significantly lower than in standardized supplements, making dietary sources insufficient for achieving the metabolic effects demonstrated in clinical studies. Standardized bitter orange extracts are used in supplements to provide consistent, research-backed dosages.

### Is synephrine safe to take with common medications like blood pressure or heart medications?

Synephrine has minimal cardiovascular effects and does not significantly raise blood pressure in clinical studies, making it generally safer with cardiac medications than ephedrine. However, because synephrine acts as a β1-receptor agonist, individuals taking beta-blockers or other adrenergic medications should consult a healthcare provider before use. Interactions are unlikely but warrant professional review given the mechanism of action.

### Who should avoid taking synephrine supplements?

Individuals with untreated hypertension, hyperthyroidism, anxiety disorders, or those sensitive to stimulants should avoid synephrine due to its sympathomimetic properties. Pregnant and nursing women lack sufficient safety data and should not use synephrine supplements. People taking monoamine oxidase inhibitors (MAOIs) or other serotonergic medications should also avoid synephrine without medical clearance.

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*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
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