Bitter and Spicy Substances in Plants

Bitter Substances

Bitter substances are widespread in nearly all plant species, with high concentrations in plants like gentian, chicory, and dandelion. They are often accompanied by compounds such as mucilage, essential oils, and tannins, contributing to their bitter taste. Bitter substances are classified into terpene and non-terpene types. Terpene bitter substances, such as iridoids and secoiridoids, derive from monoterpenes. Sesquiterpene-derived bitter substances are found in the Asteraceae family, while diterpene bitter substances occur in sage and horehound. Cucurbitacins from ivy are examples of triterpene bitter substances. Non-terpene bitter substances include those found in hops, oranges, lemons, the trisaccharide sugar gentianose, and various alkaloids.

The perception of bitter taste results from the stimulation of bitterness receptors at the base of the tongue. These receptors, located in taste buds, regenerate every six to eight days. Adults have approximately 2,000 taste buds, but their number decreases with age, reducing taste sensitivity. Factors such as smoking, stress, pregnancy, and excessive medication use can alter sensitivity to bitterness. Bitter substances regulate digestive tract motility and gland secretion through reflex mechanisms. Signals from receptors to digestive glands are transmitted by hormones like gastrin and secretin. In the digestive tract, bitter substances primarily act through their taste, reflexively increasing salivary gland secretion via the nervous system and boosting hydrochloric acid and pepsin production in the stomach. Upon reaching the stomach, they stimulate gastrin production, enhancing digestive gland secretion, particularly in the pancreas, and promoting stomach and intestinal motility.

Bitter substances enhance food utilization and stimulate digestion. Their effects are more pronounced in patients, significantly increasing gland secretion, while in healthy individuals, the increase is subtle. They are used in tonics to boost appetite in cases of weakness, anemia, convalescence, and geriatric care. Teas with bitter substances, not overly hot, should be consumed in small sips at least 30 minutes before meals. Many spices added to fatty, hard-to-digest foods aid digestion similarly.

In folk medicine, bitter substances are also used to reduce fever, though limited research exists due to the availability of synthetic drugs. Medicinal plants containing both bitter substances and essential oils improve liver and bile function, alleviate digestive cramps, and enhance fluid excretion.

Spicy Substances

Spicy substances are less commonly categorized as a distinct group, though their collective effects are well-known. Chemically, they include phenolic compounds (e.g., myristicin, elemicin, isoeugenol, asarone, safrole), amides in pepper and paprika, mustard oils in cruciferous plants, and sulfide compounds in various onions. Stimulation of temperature and pain receptors causes a spicy taste and sensation. Some spicy substances act as local anesthetics, others cause skin inflammation due to strong irritation, and some exhibit antibiotic and bactericidal effects.

Spicy substances stimulate saliva secretion and reflexively enhance stomach and intestinal peristalsis. Certain spicy substances also stimulate the respiratory and vasomotor centers. When taken internally, they improve digestion and alleviate bloating. Externally, they are used for rheumatic and muscular conditions by rubbing into the skin, causing irritation that triggers tissue hormone secretion and localized inflammation. This irritation leads to the release of internal mediators, which support the body’s defense mechanisms and increase corticoid hormone production, aiding in the treatment of inflammatory processes and muscle-related rheumatic conditions.

Mustard oils, which are sulfur-containing glycosides, exist in plants in non-volatile forms. When plant tissue is damaged, the enzyme myrosinase converts glycosides into volatile mustard oils with a pungent odor and non-volatile substances with a sharp smell. Beyond their effects on digestion and skin, volatile mustard oils exhibit strong antibacterial properties.