Bitter substances

Bitter substances (amara) are chemical (generally naturally occurring) compounds that are used solely because of their bitter taste. The corresponding drugs are called bitter drugs. Bitter substances are perceived via bitter substance receptors.

Bitter substances do not have a uniform chemical structure. Their classification as "bitter substance" is based solely on their bitter value.
Natural bitter compounds are found in numerous plants. This property is already partly expressed by their names: bitter-sweet stem, bitter orange syrup, bitter almond oil, bitter clover, bitter thistle, etc.

Bitter substances are also found in: angelica, hops, olive leaf, myrrh, ratanhia, yarrow, centaury, willow (Salix species), wormwood.

Bitter drugs like gentian, wormwood and centaury are used as medicinal plants because of their bitter substances.

Bitter substances cause an increase in gastrointestinal secretion and stimulate the appetite. Bitter substances are also said to have spasmolytic, anti-inflammatory, antimycotic and antibacterial effects.
Aromatic bitter compounds (Amara aromatica) are used in various forms. Spices like basil, rosemary, anise, fennel, caraway, dill and coriander. They are characterised by the presence of essential oils.

Most bitter substances (listed here as examples) are found in the terpenes (sesquiterterpenes, di- and triterpenes).

• Limonine (triterpene) in citrus species
• Quassin (Tripterpene) in Quassia amata the tropical bitter wood
• Artabsin (sesquiterpene) in artemisia species

Not belonging to the terpene group:

• quinine (alkaloid) obtained from the quininamide
• Naringin (flavonoid) in grapefruits
• Neohesperidine (flavonone glycoside) in citrus species

In scientific medicine, the use of bitter substances is recommended to stimulate the appetite, e.g. in cases of achylia or anorexia, as well as in sicca symptoms. The bitter substance in Quassia amara is used externally in seborrhoeic eczema and rosacea.

1. Diehl C et al (2013) Efficacy of topical 4% Quassia amara gel in facial seborrheic dermatitis:a randomized, double-blind, comparative study. J Drugs Dermatol 12:312-315.
2. Ferrari A et al(2011) Evaluation of the efficacy and tolerance of a topical gel with 4% quassia extract in the treatment of rosacea. J Clin Pharmacol 52:84-88.
3. Peters HP et al (2016) The effect of two weeks ingestion of a bitter tastant mixture on energy intake in overweight females. Appetite 107:268-273.