Chemical families

Question 1

Aldehydes

Answer 1

Key Features:
- Always ends in ‘al’ or ‘aldehyde’. e.g. citral or benzaldehyde. Contain a C=O (carbonyl carbon) group.
- Formed by the oxidation of alcohols, either by the plant, by the distillation process or by the air.
- Antiviral, anti-inflammatory, anti-fungal, antispasmodic, antibacterial, anti-microbial, vasodilator and hypotensive, calming to the nervous system (except cinnamaldehyde).
- Often have a fresh citrus aroma. They are responsible for the citrus-like fragrance of melissa, lemongrass and citronella.
Safety:
- Can be irritating to the skin and mucous membranes, especially if oxidised (citral is a common aldehyde that can cause irritation).
- Blend with monoterpenes to help reduce the potential for irritation.
- Can cause allergic reaction.
- Unstable and oxidise easily so store in a cool, dark place.
Oils reach in Aldehydes:
- Lemon Eucalyptus, Lemongrass, Melissa, Neroli.

Question 2

Esters

Answer 2

Key Features:
- Usually ends with ‘ate’ or the word ‘ester’ is included. e.g acetate, formate, angelate.
- Antispasmodic, anti-fungal, anti-inflammatory, cicatrizant, calming to the nervous system, balancing and emotionally uplifting, adaptogenic, sedative.
- Generally have a fruity and fragrant odour (popular in perfumery).
Safety:
- When diluted, esters are generally safe for topical use.
- Exceptions are: methyl salicylate (nephrotoxic) and sabinyl acetate, which are oral toxins, dermal irritants and abortifacient.
- Acetate esters in large quantities have been shown to bring on epileptic fits.
- Formate esters can overstimulate the heart rate.
Oils reach in Esters:
- Bergamot, Cardamom, Clary Sage, Geranium, Hemlock, Jasmine, Lavender, Roman Chamomile, Siberian Fir, Spruce, Ylang Ylang.

Question 3

Ethers

Answer 3

Key Features:
- Often contain the word ‘ether’ or end in ‘oxy’ or ‘ole’.
- analgesic, antimicrobial, highly antispasmodic.
Safety:
- Large doses can be neurotoxic which can cause convulsions and death.
- Safrole is nephrotoxic and has liver carcinogenic effects.
Oils reach in Ethers:
- Basil, Nutmeg.

Question 4

Ketones

Answer 4

Key Features:
- Known by their common name – e.g. camphor – or often end in ‘one’. Have C=O (carbonyl carbon) functional group bonded to two hydrocarbon radicals.
- Formed by the oxidation of alcohols.
- Mucolytic, analgesic, cooling, neurotoxic, abortifacient.
- Some ketones are thought to help scar and wound healing (cicatrizant).
Safety:
- They have to be assessed on an individual basis as some are highly toxic whereas others are not considered to be hazardous.
- E.g highly toxic: Thujone (neurotoxic, psychotropic) and camphor (neurotoxic, can overstimulate the central nervous system and cause convulsions).
- E.g non toxic: menthone, verbenone, vetivone, fenchone, carvone, piperitone, jasmone, turmerone & italidone.
- Resistant to being metabolised by the liver.
Oils reach in Ketones:
- Cistus (Rock Rose), Peppermint, Spearmint, Rosemary.

Question 5

Monoterpenes

Answer 5

Key Features:
- Molecular formula is C10H16
- All monoterpene hydrocarbons end in ‘ene’.
- Analgesic, slightly antiseptic, mild antiviral, mild antibacterial, decongestant, some considered anti-inflammatory, quenching (reducing the irritation effects of aldehydes like citral).
Safety:
- The distillation can affect the level of monoterpenes. E.g high temperature and pressure tend to create higher monoterpene levels whereas low temp/pressure tends to create higher alcohol ester content.
- Oxidise quickly and extensively and can cause skin irritation or sensitisation if oxidised.
Oils reach in Monoterpenes:
- Balsam Fir, Bergamot, Black Pepper, Cistus (Rock Rose), Cypress, Frankincense, Grapefruit, Hemlock, Juniper Berry, Kunzea, Lemon, Lime, Nutmeg, Opopanax, Orange, Palo Santo, Siberian Fir, Spruce, Pine.

Question 6

Monoterpenols

Answer 6

Key Features:
- Alcohols, all end in ‘ol’. Contain an alcohol -OH attached to a monoterpene group.
- Antiseptic, antibacterial, anti-fungal, antiviral, vasoconstrictive, skin nourishment, inflamed skin, immune system stimulants.
- Pleasant uplifting fragrance. Support emotional balance.
- Generally considered stimulating but linalool has a sedative effect.
Safety:
- Most monoterpenols have very low toxicity and are generally safe for topical use (when diluted with a carrier) and not known to be irritants except menthol.
- Menthol should not be used or inhaled by young children.
- Menthol-rich oils should be avoided by anyone advised to avoid antimalarials, sulfonamides, chloramphenicol, streptomycin or aspirin.
Oils reach in Alcohols:
- Basil, Clary Sage, Fragonia, Geranium, Lavender, Marjoram, Neroli, Palmarosa, Peppermint, Petitgrain, Rose, Tea Tree, Thyme (linalol), Xanthoxylum.

Question 7

Oxides

Answer 7

Key Features:
- Usually end in ‘ole’, 1,8-cineole (Eucalyptol) is the most common
- Expectorant, exocrine stimulant for respiratory system glands, mucolytic, mentally stimulating when inhaled, analgesic and anti-inflammatory agent for muscular and respiratory systems.
Safety:
- Asthma sufferers need to take care with 1,8-cineole as it can trigger an attack.
- Possible skin irritation and sensitisation, especially with young children.
Oils reach in Oxides:
- Cardamom, Eucalyptus, Fragonia, Laurel Leaf, Ravintsara, Rosemary.

Question 8

Phenols

Answer 8

Key Features:
- End in ‘ol’ like alcohols. To differentiate between the two, check structure diagram (they have the -OH attached to a benzene ring).
- Anti-infectious, antiseptic, germicidal, antimicrobial, antibacterial, highly anti-infectious, stimulants to both nervous and immune systems, Eugenol is antispasmodic and anticoagulant.
Safety:
- Skin and mucous membrane irritants.
- Products with high numbers of phenols should only be used topically in very low dilutions for short periods of time.
- Do not use in the bath.
- Use in small amounts in blends for diffusion (max 10%)
- Do not use products high in eugenol if you have clotting disorders.
Oils reach in Phenols:
- Cinnamon, Clove, Oregano, Thyme, Tulsi (Holy Basil).

Question 9

Sesquiterpenes

Answer 9

Key Features:
- Molecular formula is C15H24
- End in ‘ene’, vast properties of this compound group, best to assess each constituent on an individual basis as they can have unique effects including but not limited to the below.
- Anti-inflammatory, antiphlogistic, antiseptic, antibacterial, calming, some are analgesic, cleansing, pain relieving, energetically centering.
Safety:
- Generally don’t have key safety concerns.
- Some could be irritating, especially if oxidised or if you have sensitive skin.
Oils reach in Sesquiterpenes:
- Black pepper, Copaiba, Cedarwood, Chamomile, Ginger, Helichrysum, Manuka, Melissa, Myrrh, Opopanax, Patchouli, Spikenard, Vetiver, Ylang Ylang.

Question 10

Sesquiterpenols

Answer 10

Key Features:
- Alcohols, end in ‘ol’, containing an alcohol -OH attached to a sesquiterpene group.
- Vast properties of this compound group, best to assess each constituent on an individual basis as they can have unique effects including but not limited to the below.
- Anti-inflammatory, antiphlogistic, antiviral, bacteriostatic, antibacterial, antimicrobial, grounding, decongestant,
generally sedative, skin healing.
Safety:
- Generally don’t have key safety concerns.
Oils reach in Sesquiterpenols:
- Carrot seed, Cedarwood, German Chamomile, Ginger, Patchouli, Hawaiian Sandalwood, Vetiver.