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(Juniper) Juniperus communis leaves and berries

A Deep Dive Guide to Extraction, Formulation, and Quality Control

This comprehensive guide explores the scientific principles underlying herbal medicine preparation. We’ll examine extraction chemistry, solvent selection, bioavailability optimisation, quality control, and advanced formulation strategies that transform simple plant material into effective therapeutic preparations.

Table of Contents

  1. The Fundamental Science of Extraction
  2. Solvent Chemistry and Selection
  3. Method 1: Infusions and Decoctions – Water Extraction
  4. Method 2: Tinctures – Alcohol Extraction
  5. Method 3: Infused Oils – Lipid Extraction
  6. Method 4: Salves and Topical Preparations
  7. Method 5: Syrups and Electuaries
  8. Advanced Extraction Techniques
  9. Formulation Principles and Synergy
  10. Quality Control and Standardisation
  11. Bioavailability Enhancement Strategies
  12. Dosing Calculations and Safety

The Fundamental Science of Extraction

Core Principles

Extraction is the process of separating bioactive phytochemicals from plant material using a solvent (menstruum). The fundamental principle is selective solubility: different compounds dissolve in different solvents based on their chemical properties.

The Solubility Rule: “Like Dissolves Like”

This principle is central to all herbal extraction:

Polar solvents (water, alcohol, vinegar) dissolve polar compounds:

Non-polar solvents (oils, fats) dissolve non-polar compounds:

Amphiphilic solvents (alcohol, glycerine) dissolve both:

Extraction Efficiency: Key Variables

1. Surface Area

Principle: The more plant surface exposed to solvent, the faster and more complete the extraction.

Why: Diffusion occurs at the plant-solvent interface. More interface = faster diffusion.

Practical Application:

2. Temperature

Principle: Increased temperature speeds molecular motion and diffusion.

Why: Heat energy increases kinetic energy of both solvent and solute molecules, facilitating dissolution.

Trade-offs:

Critical temperatures:

3. Time

Principle: Diffusion is time-dependent. Given enough time, equilibrium is reached where solvent is saturated with extracted compounds.

Why: Compounds must diffuse from inside plant cells → through cell walls → into bulk solvent. This takes time.

Practical application:

4. Agitation

Principle: Movement disrupts the boundary layer around plant material, bringing fresh solvent into contact with plant surfaces.

Why: Without agitation, a concentrated layer forms around plant material, slowing further extraction (concentration gradient decreases).

Practical application:

5. Solvent-to-Material Ratio

Principle: More solvent allows more complete extraction.

Why: A larger volume of solvent can dissolve more compounds before becoming saturated.

Common ratios:

Solvent Chemistry and Selection

Water: The Universal Polar Solvent

Chemical Properties:

What Water Extracts:

Minerals:

Polysaccharides:

Tannins:

Water-Soluble Vitamins:

Some Flavonoids:

Limitations:

Ethanol (Alcohol): The Versatile Amphiphilic Solvent

Chemical Properties:

What Alcohol Extracts:

Everything water extracts, PLUS:

Alkaloids:

Resins:

Volatile Oils:

Glycosides:

Alcohol Percentage and Selectivity:

Lower alcohol (25-40%):

Medium alcohol (40-60%):

Higher alcohol (60-95%):

The Fresh Herb Problem:

Fresh herbs contain 70-90% water. When you add fresh herbs to 40% alcohol:

Alcohol as Preservative:

Mechanism: Alcohol denatures proteins and disrupts cell membranes of microorganisms.

Minimum preservation concentration:

Glycerine: Sweet Alternative Solvent

Chemical Properties:

What Glycerine Extracts:

Similar to water:

Limitations:

Advantages:

Optimal Concentration:

Preservation:

Vinegar: Acid Extraction

Chemical Properties:

What Vinegar Extracts:

Particularly good for:

Why Apple Cider Vinegar (ACV):

Best applications:

Limitations:

Oils: Lipophilic Extraction

Chemical Properties:

What Oils Extract:

Fat-soluble compounds:

Does NOT extract:

Carrier Oil Selection:

Olive Oil:

Sweet Almond Oil:

Sunflower Oil:

Jojoba Oil:

Coconut Oil:

Method 1: Infusions and Decoctions – Water Extraction

The Chemistry of Water Extraction

Standard Infusion (Hot Water):

Temperature: 90-100°C (just off boil)

Extraction sequence:

  1. Immediate (0-2 minutes): Volatile oils begin to dissolve and evaporate
  2. Early (2-10 minutes): Tannins, flavonoids, simple sugars extract
  3. Extended (10-30 minutes): Polysaccharides (mucilage) hydrate and release
  4. Long infusion (4-8+ hours): Minerals, deeply bound compounds extract

Why covering matters:

Volatile oil retention:

Experimental evidence:

Cold Water Infusion (Overnight):

Temperature: Room temperature (15-25°C)

What it’s best for:

How it works:

Limitations:

Nourishing Infusion (Long Steep for Minerals):

Method: Large amount of herb (250ml/1 cup) in 1 litre water, steep 4-8 hours (covered)

What this does:

Why it works:

Decoction: Heat-Intensive Extraction

Temperature: 90-100°C (simmering)

Time: 15-45 minutes

What it’s for:

Why it works:

Trade-offs:

Benefits:

Costs:

When NOT to use:

Optimal decoction technique:

  1. Start with cold water: Allows gradual extraction as temperature rises
  2. Bring to boil, then reduce: Gentle simmer, not hard boil
  3. Cover tightly: minimise volatile loss (though significant loss is inevitable)
  4. Strain while hot: Some compounds re-absorb into plant material as it cools

Volume reduction:

Traditional decoctions reduce liquid by 1/3 to 1/2:

Bioavailability Considerations

Tannin-Iron Interaction:

Problem: Tannins bind non-heme iron (plant iron), reducing absorption.

Solution:

Polysaccharide Absorption:

Mucilaginous herbs (plantain, marshmallow) can slightly reduce absorption of other compounds by coating gut lining.

Solution:

Method 2: Tinctures – Alcohol Extraction

Tincture Ratios: Understanding 1:5, 1:2, etc.

Ratio notation: Herb: Solvent (by weight: volume)

1:5 tincture:

1:2 tincture:

1:10 tincture:

Folk Method vs. Weight-to-Volume:

Folk method (described in Everyperson Guide):

Weight-to-volume (professional standard):

Alcohol Percentage Selection: The Science

For different compound classes:

Resins & Volatile Oils → 60-95% alcohol

Tannins & Glycosides → 25-50% alcohol

Alkaloids → 50-70% alcohol

General-purpose → 40-60% alcohol

Calculating Alcohol Dilution

Formula: Cā × Vā = C₂ × V₂

Where:

Example: Make 500ml of 60% alcohol from 95% alcohol

(0.95)(Vā = (0.60)(500)
Vā = 315.8ml

Recipe:

Proof vs. Percentage:

Extraction Kinetics in Tinctures

Phase 1 (Week 1): Rapid extraction of readily soluble compounds

Phase 2 (Weeks 2-4): Slower extraction of less accessible compounds

Phase 3 (Weeks 5-6+): Equilibrium approached

Why shake daily:

Disrupts concentration gradient:

Breaks up compacted material:

Optimal shaking:

Marc to Menstruum Ratio Optimisation

Underfilled jar (too much solvent):

Overfilled jar (too much herb, not enough solvent):

Optimal:

Glycerite Formulation

Optimal ratio: 75% glycerine, 25% water (by volume)

Why not 100% glycerine:

Method:

  1. Fill jar 1/3 to 1/2 with dried herbs
  2. Mix 3 parts glycerine + 1 part water
  3. Pour over herbs (cover completely)
  4. Shake daily for 4-6 weeks
  5. Strain

Extraction efficiency compared to alcohol:

Vinegar Tincture (Acetract)

Optimal vinegar: Raw, unfiltered apple cider vinegar (5-7% acetic acid)

What it extracts well:

Ratio: Same as alcohol tinctures (1:5 for dried herbs)

Time: 2-4 weeks (faster than alcohol — acidity enhances extraction)

Preservation: Acetic acid provides some preservation, but less than alcohol

Best herbs for vinegar:

Container note: Use plastic lid or place plastic wrap between liquid and metal lid (vinegar corrodes metal)

Method 3: Infused Oils – Lipid Extraction

The Critical Safety Issue: Water and Botulism

Clostridium botulinum:

  • Anaerobic bacteria (grows without oxygen)
  • Produces botulinum toxin (one of the most deadly natural toxins)
  • Spores are everywhere (soil, plants)

Conditions for growth:

  • Anaerobic environment: Oil creates this (excludes oxygen)
  • Low acid: pH > 4.6 (oil is neutral pH ~7)
  • Moisture: Water present
  • Temperature: 3-43°C (normal storage temp)

How fresh herbs create risk:

  • Fresh herbs contain 70-90% water
  • This water is released into oil
  • Creates perfect environment for C. botulinum

Prevention strategies:

Strategy 1: Eliminate water (dried herbs only)

Strategy 2: Wilt fresh herbs

Strategy 3: Heat method (pasteurisation)

Signs of contamination:

Oil Selection: Chemistry of Stability

Fatty acid composition determines stability:

Saturated fats (most stable):

Monounsaturated fats (moderately stable):

Polyunsaturated fats (least stable):

Oxidation process:

  1. Initiation: Light, heat, or oxygen starts free radical cascade
  2. Propagation: Free radicals attack double bonds in fatty acids
  3. Termination: Produces rancid-smelling compounds (aldehydes, ketones)

Antioxidants slow oxidation:

Extraction Mechanisms in Oil

Diffusion-driven process:

Solar method efficiency:

Temperature: 20-35°C (warm windowsill)
Time: 2-4 weeks
Mechanism: Slow, gentle diffusion

Advantages:

Disadvantages:

Heat method efficiency:

Temperature: 50-80°C (optimal ~60°C)
Time: 2-4 hours
Mechanism: Heat accelerates diffusion ~10-20x

Advantages:

Disadvantages:

Optimal heat method protocol:

  1. Temperature control: Use thermometer, maintain 60-70°C
  1. Duration: 2-4 hours sufficient for most herbs
  2. Visual indicators:
  1. Strain while warm: Easier flow, more complete drainage

Carrier Oil Bioavailability

Penetration vs. Occlusion:

Penetrating oils (smaller molecules):

Occlusive oils (larger molecules):

For salves:

Method 4: Salves and Topical Preparations

Beeswax Chemistry and Function

Chemical composition:

Why beeswax thickens oil:

Mechanism: Wax esters crystallise as they cool, forming a matrix that traps liquid oil.

Process:

  1. Melted state (>65°C): Wax and oil form homogeneous liquid
  2. Cooling (40-65°C): Wax esters begin crystallising
  3. Solid state (<40°C): Crystalline wax matrix holds oil in semi-solid form

Consistency control:

More beeswax = firmer salve

Temperature effects:

Alternative Thickeners

Vegan alternatives to beeswax:

Candelilla wax:

Carnauba wax:

Emulsification: Making Creams vs. Salves

Salve: Oil + wax only (no water)

Cream: Oil + water emulsion

Basic emulsion chemistry:

Problem: Oil and water don’t mix (immiscible)

Solution: Emulsifier (surfactant) creates stable mixture

Emulsifier structure:

Common emulsifiers:

Basic cream formula (advanced):

Why preservative is essential in creams:

This guide focuses on salves (oil-only):

Bioenhancers in Topical Applications

Compounds that enhance skin penetration:

Essential oils (small amounts):

Dimethyl sulfone (MSM):

Vitamin E:

Method 5: Syrups and Electuaries

The Science of Preservation by Sugar

Osmotic Pressure:

At high concentrations (>65% sugar), water activity (aw) drops below 0.85.

Water activity (aw):

Mechanism:

Optimal sugar concentration:

Honey vs. Sugar

Honey advantages:

Additional antimicrobial properties beyond sugar:

Enzyme content:

Nutritional content:

Disadvantages:

Sugar (sucrose) advantages:

NZ Honey Options:

Extraction in Honey: The Long Method

Honey as solvent:

Honey can extract water-soluble compounds because it contains ~17-20% water.

Mechanism:

What honey extracts well:

What honey doesn’t extract:

Optimal honey infusion method:

  1. Fill jar 1/3 to 1/2 with dried herbs (or more with fresh)
  2. Pour raw honey over herbs
  3. Stir to remove air pockets (use chopstick to push down herbs)
  4. Seal and let sit 2-4 weeks
  5. Warm very gently (optional — makes straining easier) at <40°C
  6. Strain (or leave herbs in)

Shelf life:

Electuaries: Powdered Herb + Honey

Definition: Thick paste of powdered herb mixed with honey or syrup

Ratio: Typically 1 part powdered herb to 2-3 parts honey (by weight)

Advantages:

Disadvantages:

Best herbs for electuaries:

Method:

  1. Grind dried herb to fine powder (coffee grinder, mortar and pestle)
  2. Mix powder with honey (start with less honey, add more to achieve paste consistency)
  3. Store in jar
  4. Take 5ml (1 teaspoon) as needed

Advanced Extraction Techniques

Percolation: Continuous Solvent Flow

Principle: Fresh solvent continuously flows through plant material, maintaining maximum concentration gradient.

How it works:

  1. Plant material packed in percolator (cone-shaped vessel)
  2. Solvent added at top, drips through herb bed
  3. Extract collected at bottom
  4. Key: Solvent at top is always “fresh” (not yet saturated)

Advantages:

Disadvantages:

Home application:

Ultrasonic Extraction

Principle: Ultrasonic waves create cavitation (bubble formation and collapse) that disrupts plant cell walls.

How it works:

Advantages:

Disadvantages:

Home application:

Freeze-Thaw Extraction Enhancement

Principle: Freezing disrupts plant cell walls (ice crystals rupture cells).

How it works:

  1. Fresh plant material + solvent in jar
  2. Freeze overnight (-18°C or colder)
  3. Thaw at room temperature
  4. Repeat 2-3 freeze-thaw cycles
  5. Then proceed with normal maceration

Advantages:

Disadvantages:

Best applications:

Formulation Principles and Synergy

The Art of Combination

Why combine herbs:

  1. Synergy: Combined effect greater than sum of individual parts
  2. Address multiple symptoms: Complex conditions need multifaceted approach
  3. Enhance bioavailability: Some herbs enhance absorption of others
  4. Balance actions: Correct unwanted side effects

Synergy: Mechanisms

Pharmacokinetic synergy:

Example: Turmeric + Black Pepper

Pharmacodynamic synergy:

Example: Chamomile + Lemon Balm (sleep blend)

Additive vs. Synergistic:

True synergy is less common than claimed, but does occur with specific combinations.

Traditional Formulation Framework

Primary herb (50-70% of blend):

Supporting herbs (20-30%):

Corrective herbs (5-10%):

Example: Digestive Upset Formula

Primary: Peppermint (50%) — carminative, antispasmodic
Supporting: Chamomile (30%) — antispasmodic, anti-inflammatory, nervine
Supporting: Ginger (15%) — carminative, warming, digestive stimulant
Corrective: Fennel (5%) — carminative, pleasant flavour

Rationale:

Ratio Calculation for Blended Tinctures

Two approaches:

Approach 1: Simplers Method

Example:

Approach 2: Combined Maceration

Example:

Which to use:

Taste Balancing

Categories of taste:

Bitter:

Pungent/Spicy:

Sweet:

Strategies for bitter tinctures:

  1. Add to juice: Strong-flavoured juice (grape, cranberry) masks bitterness
  2. Honey: Add 5-10ml honey to dose in water
  3. Glycerine: Add small amount of glycerine to tincture (10-20%)
  4. Aromatic herbs: Add pleasant-tasting herbs (fennel, mint) to blend

For children:

Quality Control and Standardisation

Assessing Quality

For dried herbs:

Visual inspection:

Smell:

Taste:

For finished preparations:

Visual:

Smell:

Stability over time:

Shelf Life Reality

Official vs. Practical:

Official shelf life (conservative, for liability):

Practical shelf life (when properly stored):

Key: Trust your senses. If it smells/looks/tastes good, it likely is good.

Bioavailability Enhancement Strategies

The Bioavailability Problem

Definition: Bioavailability is the fraction of an administered substance that reaches systemic circulation unchanged.

For herbal compounds, bioavailability is often low due to:

  1. Poor aqueous solubility: Many phytochemicals don’t dissolve well in water
  2. Poor lipid solubility: Can’t cross cell membranes easily
  3. First-pass metabolism: Liver metabolises compounds before they reach circulation
  4. Efflux transporters: Pump compounds back out of cells (P-glycoprotein)

Enhancement Strategy 1: Co-administration

Black Pepper (Piperine) as Universal Enhancer:

Mechanism:

Evidence:

Application:

Enhancement Strategy 2: Lipid Formulations

Fat-soluble compounds absorb better with dietary fat:

Mechanism:

Application:

Enhancement Strategy 3: Timing and Food

With food vs. Empty stomach:

Empty stomach advantages:

With food advantages:

Herb-specific recommendations:

Dosing Calculations and Safety

Standard Adult Dosing

Tincture dosing:

Tea dosing:

Body Weight Adjustments:

Clark’s Rule (approximate):
Dose = (Weight in kg ÷ 70) × Adult Dose

Example: 50kg person
Dose = (50 ÷ 70) × 4ml = 2.9ml (round to 3ml)

Pediatric Dosing

Never guess with children — use established guidelines:

Age-based approximations:

Better: Young’s Rule (weight-based)
Dose = [(Age in years) ÷ (Age + 12)] × Adult Dose

Example: 6-year-old
Dose = [6 ÷ 18] × 4ml = 1.3ml (round to 1.5ml)

Important pediatric considerations:

Safety Margins

Therapeutic Index: Ratio of toxic dose to effective dose

Herbs generally have wide therapeutic index:

  • Effective dose: 2-4ml tincture
  • Toxic dose: Often 50-100x effective dose (or higher)
  • Much safer than pharmaceuticals (narrow therapeutic index)

This doesn’t mean herbs are risk-free:

  • Drug interactions can be serious
  • Allergic reactions possible
  • Contraindications matter
  • Quality/identity crucial

Conclusion

Making herbal medicines is both ancient art and modern science. Understanding the principles — extraction chemistry, solubility, bioavailability, synergy — elevates your practice from following recipes to creating sophisticated, effective formulations.

The methods detailed here represent centuries of empirical knowledge now understood through phytochemistry, pharmacology, and materials science. Every jar of tincture is an applied chemistry experiment. Every salve is an emulsion engineered for optimal delivery.

Respect the science. But also respect the intuitive wisdom that comes from doing this work with your hands, observing your preparations, and learning from each batch.

Welcome to the intersection of tradition and science. Welcome to the art and science of herbal medicine-making.

Sources & References

Extraction Science

Azmir, J., et al. (2013). Techniques for extraction of bioactive compounds from plant materials: A review. Journal of Food Engineering, 117(4), 426-436.

Altemimi, A., et al. (2017). Phytochemicals: Extraction, isolation, and identification of bioactive compounds from plant extracts. Plants, 6(4), 42.

Zhang, Q. W., et al. (2018). Methods for the detection and determination of bioactive compounds in biological samples. Chinese Medicine, 13, 20.

Bioavailability

Shoba, G., et al. (1998). Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. Planta Medica, 64(4), 353-356.

Rein, M. J., et al. (2013). Bioavailability of bioactive food compounds: A challenging journey to bioefficacy. British Journal of Clinical Pharmacology, 75(3), 588-602.

Tinctures & Extraction Methods

Bone, K., & Mills, S. (2013). Principles and Practice of Phytotherapy: Modern Herbal Medicine (2nd ed.). Churchill Livingstone.

Green, J. (2000). The Herbal Medicine-Maker’s Handbook: A Home Manual. Crossing Press.

Essential Texts

Hoffmann, D. (2003). Medical Herbalism: The Science and Practice of Herbal Medicine. Healing Arts Press.

Mills, S., & Bone, K. (2005). The Essential Guide to Herbal Safety. Churchill Livingstone.

Williamson, E. M., Driver, S., & Baxter, K. (Eds.). (2013). Stockley’s Herbal Medicines Interactions. Pharmaceutical Press.

Disclaimer: This guide is for educational purposes only and is not medical advice. Herbal preparations can interact with medications, cause allergic reactions, and may be contraindicated in certain health conditions. Always consult qualified healthcare practitioners before using herbal medicines, especially if you are pregnant, nursing, taking medications, or have medical conditions. You are solely responsible for correct plant identification, safe preparation practices, and appropriate use. The information presented represents current scientific understanding, which continues to evolve.

For medical emergencies, call 111. For poisoning information, contact the National Poisons Centre: 0800 764 766.

Note on Pricing: All prices mentioned in this guide are approximate and based on New Zealand suppliers as of December 2025. Prices vary by supplier, season, and market conditions. We recommend checking current prices with your local suppliers.

The Public Herbarium is built on a foundation of scientific integrity, transparency, and care. Research sources are referenced throughout the site wherever possible. Content creation is assisted by AI tools and carefully reviewed for accuracy.