Pharmacognosy with the Basics of Plant Biochemistry - Kovalyov V. M. 2004

General Section
Variability of the Chemical Composition of Medicinal Plants

A plant is a biological system and is therefore characterized by a complex of interacting biochemical and molecular-biological structures. Based on their degree of Organization, the main levels of plant biological systems are distinguished as follows: Cell, tissue, organ, Organism, population, and biocenosis. Structurally, a biological system is multilevel and composed of subsystems, which, in turn, are biological systems themselves. For example, the subsystems of a plant are Organs, those of organs are Tissues, of tissues are Cells, and of cells are subcellular structures. A plant biological system is an open, self-regulating entity that continuously exchanges energy, matter, and information with its external environment.

The chemical composition of plants is characterized by Variability—The ability to acquire new chemical traits or lose existing ones under METABOLISM/18.html">The Influence of various factors. This variability can be genotypic (hereditary), phenotypic (non-hereditary), individual, or group-based.

Genotypic variability includes changes in a plant's chemical composition caused by alterations in its genotype. Metabolic variability has been proven to exist even within a single species, determined by the organism's hereditary foundation and the conditions under which ontogeny takes place. Such related subspecies are referred to as “chemotypes” or “chemoraces.” Variability in chemical composition is frequently observed in plants containing Water/23.html">Essential Oils and affects the main constituents of these oils. A clear example is the occurrence of azulene-containing and non-azulene “races” in chamomile (*Chamomilla recutita*) and yarrow (*Achillea millefolium*).

The formation and accumulation of BIOLOGICALLY ACTIVE SUBSTANCES in medicinal plants is a dynamic process closely tied to developmental stages and environmental factors. Throughout ontogeny (individual development), each cell initially grows, reaches its maximum size, performs its specific Functions for a period, and eventually dies. Ontogeny is accompanied by characteristic shifts in metabolism. Consequently, Changes in the metabolism of Proteins, CARBOHYDRATES, and Lipids, as well as Vitamins, Enzymes, and Coenzymes, lead to alterations in secondary metabolite turnover (Alkaloids, Terpenes, Phenolic Compounds, etc.). The dynamics of active substance production in any given plant follow specific patterns governed by ontogenetic laws and depend on the plant's age and vegetative phase. Understanding this is crucial for determining the optimal harvest time for raw Materials. For instance, in The Development of the opium poppy (*Papaver somniferum*), alkaloids appear immediately after seed germination, whereas morphine emerges only In the second month. Alkaloid content peaks during the flowering phase, subsequently decreases, and disappears entirely by the first frosts.

Ontogenetic features also include the qualitative Specificity of pharmacologically active substances within taxonomic plant subdivisions (species, genera, families, classes). Certain groups of plants accumulate predominantly cardiac Glycosides, while others accumulate anthracene derivatives, and so on. The Synthesis of specific chemical compounds in phylogenetically (historically) related plant families and genera is made possible by similarities in metabolic pathways. It is well established that already at the dark reaction stage of Photosynthesis, plants are divided into three types: C₃-photosynthesizing, C₄-photosynthesizing, and Crassulacean Acid Metabolism (CAM) species. Plants that fix carbon dioxide via The Calvin Cycle (C₃ type) typically grow in temperate climates, with an optimum Temperature for CO₂ fixation of 15–20 °C. C₄ plants are widespread in tropical regions. Plants with Crassulacean acid metabolism are more commonly found in arid environments and deserts; they are sometimes referred to as CAM plants or organic acid metabolism plants. Differences in habitat influence both the biochemical properties of PLANTS AND THEIR morphological traits (such as stomatal density, the Structure and arrangement of mesophyll cells, and intercellular spaces).

A notable characteristic of plants is the uneven distribution of active substances across organs and tissues, with preferential localization in specific morphological structures. For example, in the cinchona tree (*Cinchona succirubra*), quinine accumulates in the bark, whereas in plants of the celery family (Apiaceae), essential oils are localized in the fruits. The quality and quantity of active substances can vary significantly across different Organs of the same plant. For instance, glycyrrhizic acid is predominantly deposited in the underground organs of licorice (*Radices Glycyrrhizae*), whereas other triterpene saponins are found in the aerial parts.

An even broader spectrum of chemical variability is observed in medicinal plants under the Influence of Environmental factors (growing conditions). Plant metabolism heavily depends on soil composition, mineral availability, moisture, microphytobiome, mechanical structure, and thermal properties. Some plants thrive exclusively on soils rich in calcium carbonate (calciphiles). For example, chalk-loving plants such as *Hyssopus cretaceus*, *Thymus cretaceus*, and calcicole oaks grow in areas dominated by alkaline or neutral soils. Conversely, calciphobic plants react negatively to the presence of calcium salts in the soil. Calciphobes include sphagnum mosses, lupines, tea (*Camellia sinensis*), heather (*Calluna vulgaris*), sweet chestnut, and lingonberry (*Vaccinium vitis-idaea*).

Precipitation and atmospheric humidity also affect the Qualitative and quantitative composition of plant chemicals. Excessive moisture is detrimental to xerophytes, whereas arid growing conditions are harmful to hydrophytes. Mesophytes occupy an intermediate position, being well-adapted to moisture fluctuations. Mesophytes are characterized by faster metabolism, higher growth rates, larger leaves, and overall larger plant size, which ensures high crop yields. Most cultivated cereal, forage, medicinal, and fruit-berry plants belong to this group. Mesophytes thrive best under moderate moisture, thermal, and aerial regimes, as well as adequate mineral Nutrition.

Thermal and light energy dictate the duration of the growing season, the accumulation of active substances, and the biomass of raw plant material. Every plant has an optimal heat maximum that allows it to fully complete its life cycle. Questions of thermal regimes form the foundation of medicinal plant cultivation at zonal research stations. For instance, *Salsola Richteri*, which grows wild in the desert, contains only trace amounts of alkaloids; however, when cultivated under strict agrotechnical guidelines, its alkaloid content exceeds 1.5%.

Warm weather promotes an increase in plant alkaloid content, whereas cold weather inhibits its synthesis, and frosts prevent alkaloid accumulation altogether. For example, in the Caucasus, the aerial parts of *Veratrum lobelianum*, and in Central Asia, the herb of *Anabasis aphylla*, can be grazed by animals after frosts without causing poisoning.

The influence of nutrition, light, heat, and moisture on plant metabolism is essentially The Effect of geographical factors—a complex of ecological conditions associated with geographical features such as latitude, longitude, exposure, and altitude above sea level. As the geographical environment changes, the entire complex of interrelated factors shifts, including temperature fluctuations, sunlight intensity, and UV radiation availability. Plants in southern latitudes generally accumulate higher concentrations of active substances. One need only look at the potency of poisonous plants in tropical countries.

Geographical longitude also exerts some influence on the quantity of active substances. In most cases, plants from the eastern, more continental Regions of the European mainland yield higher quantities of essential oil. It is well known that in oil-producing plants, the proportion of Fatty acids and the iodine value of the oils increase with distance from the coast deep into the mainland. The continental climate affects the saponin content in licorice: Central Asian roots contain significantly more glycyrrhizic acid than those cultivated in Spain or Italy.

Altitude above sea level significantly alters the accumulation dynamics of active substances as well. It has been proven that each species has its optimal elevation range. *Senecio platyphylloides* accumulates the highest amount of alkaloids at an altitude of 1800–2000 meters above sea level; at higher elevations, the alkaloid content declines. A similar phenomenon is observed in deadly nightshade (*Atropa belladonna*) and jointed ephedra (*Ephedra equisetina*).

When harvesting, drying, and studying the Chemical composition of Medicinal Plants, one must account for biological rhythms—cyclic fluctuations in the intensity and Nature of the plant's biological processes. The phase of these biological rhythms shifts with changes in illumination and temperature. For instance, the alkaloid content in *Lobelia inflata* fluctuates even within the course of a day: at midnight, it is 40% higher than at noon. Lancing poppy capsules (*Capita Papaveris*) in the evening yields a greater volume of opium with a higher alkaloid concentration.

The Overview of factors altering the chemical composition of medicinal plants presented here is quite general and preliminary. Their effects will be examined in greater detail when exploring specific plant groups.