Light. The importance of the intensity of light is attested by the fact that the quantity of active ingredients may greatly vary according to the geographical location. For example, in southern areas the level of active ingredients was two to three times higher, compared to northern areas. Furthermore, with more light not only does the quantity of one active ingredient increase but the plant may start producing other alkaloids as well. For instance, trials in poppy showed that besides the exclusive production of morphine, increased light resulted first in the appearance of codeine, then of thebaine. In other trials it also turned out that shading resulted in a decrease not only of essential oil in peppermint, but of menthol too.
Generally short-waved UV radiation was beneficial. In this connection primarily plants containing alkaloids (members of the Solanaceae family) reacted in a definitely positive way. Increased light intensity is also beneficial. The short wave range of visible light (i.e., blue light) had a similar effect, but besides alkaloid content, the proportion of ingredients also changed. In the case of plants containing essential oils the opposite process was observed: accumulation increased due to red light.
It was observed in several plants that exposure to long day lighting (12-16 hours) resulted in definitely higher alkaloid content, and in other plants, higher essential oil content. In the case of one Datura species it was noted that in long daylight periods scopolamine accumulation was raised and in short daylight periods hyoscyamine accumulation was greater.
Temperature. In this respect it is the optimum temperature of the given species that matters, there is no general optimum value. In certain trials it was established that plants grown at higher temperatures had higher alkaloid contents. But precisely in poppy species it was reported that in some species higher temperatures caused the accumulation of codeine rather than that of morphine. It was reported that in the case of mint, it was the mean temperature preceding intense growth and harvesting that determined essential oil content. Temperature fall resulted in the fall of essential oil content in other plants, at the same time their levels of certain other ingredients rose.
Water supply. It is a basic factor, and there are numerous ways of adapting to it. Effects influencing active ingredient production highly depend on the ecotype, in other words, it does matter whether the tests were conducted on hydrophyton or xerophyton plants. A lot of contradicting results have been published in this respect. The picture gets more complicated by the fact that if water supply and precipitation are greater, lack of light often carries more importance.
The effect of water supply varies in each case. Irrigation sometimes may increase drug content, e. g., in woolly foxglove, while scented mayweed prefers draught for essential oil production. Similarly, irrigation increased essential oil content of the rhizome of angelica, the fruit of fennel and the fruit and stem of caraway. But irrigation definitely decreased essential oil content in the flowering stem of lavender and the root and stem of parsley.
Soil. Soil affects plants in a complex way, therefore it is difficult to get accurate results in natural circumstances. There are several observations relative to the soil pH. Arnica specifically tolerates acidic soils, but cowslip, hyssop, and pheasant’s eye can be cultivated in basic soils. The essential oil content of scented mayweed and valerian is bigger on basic soils. The physiological optimum of lily of the valley is around neutral pH but it grows in acidic and basic soils as well.
As for nutrients, medium nitrogen levels are usually favourable. But it can happen that in favourable conditions, the plant’s stem and leaf production increases, which parts contain hardly any alkaloids in Solanum species, while the volume of berries, which are important from a harvesting point of view, decreases. In the case of dill, depending on whether the leaf-drug or the fruit-drug is needed, different nutrient levels are recommended.
Active ingredient production is negatively affected by herbicides, parasites and viruses, but Vinca minor, or lesser periwinkle, produces 50-200% more alkaloids under stress. Accumulation of active ingredients often takes place around flowering, or in the case of underground parts, at the end of the plant’s life-cycle.
Lunar effects. Changes and phases of the moon affect every living being on earth – plants, animals and humans alike. This fact can be liked, discarded or disregarded, but it still works that way. In organic farming lunar effects are decisive factors and are taken into consideration. These effects are naturally important in the case of medicinal plants since depending on the moon phase, active ingredients are concentrated in different parts of the plant. We will give a brief summary of these views and it is up to each future herbalist whether he or she will take them into consideration or not. Of course, it is not true that a plant harvested at a bad time would be ineffective. But it should be emphasised that plant parts harvested at the proper time are more effective.
Root parts should be harvested when the moon is full, new or waning, in spring or autumn, before sunrise or after sunset. Since the element of root plants is earth, therefore earth days –days of the signs of Capricorn, Virgo and Taurus – are most suitable for their harvesting.
Flower parts are best collected when the moon is waxing or full, slightly before noon, on a sunny day when dew already dried off. For flower plants, the air element is best, therefore days of the signs of Gemini, Libra and Aquarius are most suitable for harvesting.
Leaves should be harvested when the moon is waxing. Dewless young leaves are the best. Leaf plants correspond to the element of water; therefore the moon should be in the sign of Scorpio, Pisces or Cancer on the day of their harvesting.
For harvesting fruits the waxing moon is the best if we use them immediately. If we want to preserve them for later use, we should pick them during a waning moon. Fruits should not be collected in midday heat. Fruits correspond to the element of fire, therefore the moon should be in the signs of saggitarius, Leo or Ram when harvesting them.
2.9. 9. Collecting and preserving medicinal plants
Collection. The ground rule is that one should know the plant to be collected, its characteristics for proper identification, and similar species that it can be mixed with. The latter possibility does not present a problem when a related, similar species is also a medicinal plant, moreover they can be collected under the same drug name as per regulations. Among such an examples are small-leaved linden and large-leaved linden – although their flowering takes place at different times, that of large-leaved linden preceding the other species by even two weeks. However, both must be separated from silver linden that blooms later because the inflorescence of the latter, although very nice-smelling, can only be used for industrial purposes as its stellate hairs are allergens. Similarly, all the white-flowered yarrow species can be collected and both hawthorn species have the same medicinal value.
The situation is different with St. John’s wort species, some of which are protected species and therefore not collectible. On the other hand, they include species whose active ingredient levels are lower, so they can spoil the quality of the drug. In the case of horsetail species we have to be very cautious because several similar species are poisonous. In addition, field horsetail and marsh horsetail are often mixed together. Scented mayweed and false (or wild) chamomile may appear very similar, but while scented mayweed flowers relatively early and fades away after the ripening of the fruit, false chamomile is in flower in late summer. Naturally, one can tell scented mayweed from its nice scent and hollow receptacle, while false chamomile is scentless and has a solid receptacle.
We have to be able to identify very poisonous plants, and caution should be made not to mix them with medicinal herbs during drying or storing. We have to be able to identify protected plants too, so as not to collect them by chance.
We have to know which plant parts contain the largest amounts of the drug and which parts must be or can be collected. Naturally it includes knowledge of the flowering time in case of flower drugs because it may greatly vary.
Flowers are usually collected in full bloom but composites are harvested earlier, for instance goldenrod, because its flowers mature after harvesting and develop fruits. Elder flowers must be harvested with the pedicel, the flowers of black locust without it. In the case of mullein and dead-nettle, only the petals must be harvested, but scented mayweed and clover can be harvested with a short, 5 mm long pedicel. Often the time to harvest the drug is further specified, for instance, scented mayweed must be harvested in early flowering, while yarrow species must be harvested in full bloom.
Leaves should be fully developed, young and healthy at the time of harvesting; they should not be diseased, bitten, or populated e.g., by aphis colonies.
In the case of flowering stems, usually the top 30-50 cm should be cut, where the stem is thin and not woody. In the case of sub-shrubs like thyme, one year-old shoots are harvested. Naturally it is the size of the plant that determines the length of the part to be harvested, in the case of e. g., white horehound, the width of stem parts should not exceed 5 mm.
The roots and the rhizome can usually be harvested from autumn till spring, in October-November and in March-April. The size of the stem attached to the rhizome is also important, and these plant parts must be cleaned, washed, and sometimes peeled and cut before drying.
It is important to know the plant’s habitat as well. On the one hand, it is good to know that coltsfoot grows on banks in pioneer plant communities, while butterbur in forest and riverside communities, because it makes collection easer. On the other hand, since plants growing on roadsides may get contaminated by harmful substances, their lead and cadmium content levels may be quite high by busy roads. In extreme cases, plants have to be collected 50-100 meters further away from such roads. Unfortunately, illegal waste disposal is very common, including heavily toxic materials. These substances which are harmful to humans can be absorbed by the plants, so one must be careful not to collect flowers from, e. g., elder bushes that thrive at such places.
Drying. Hot air should be used with caution so that plant parts do not get roasted. Natural drying is always preferable, although it is more space-demanding. 1 kg dried drug can be obtained from about 5-8 kg of flower, 4-5 kg of leafy flowering stem, 3-4 kg of raw root and 1.2-1.5 kg of fruit. If drying is inappropriate, the drug may even be completely spoiled. After drying, the processes of selection, cleaning, graining, grinding and storing are also important. Distillation and cold-pressing are methods utilized to extract essential oils from species which are sensitive to heat, like e. g., the citrus family.
Cultivation of medicinal plants
- The ratio of biologically active special substances is less than 1%.
- Only those parts that contain active ingredients can be used (leaf, fruit, bark, seed, etc).
- Fresh parts are usually not suitable, they are used only in dried or tincture form.
- Plant drugs are consumed in very small quantities.
The same plant can be a medicinal plant, a spice plant and it may contain essential oils at the same time, like for instance mint. Furthermore, it can also be a fodder crop, a weed and an ornamental, depending on where it grows and what it is used for. Globally, 35-45% of pharmaceutical drugs are plant-based, for the following reasons.
- The active ingredient is unknown or too complicated, therefore cannot be synthesised.
- The drug’s effect mechanism is more complex, e. g., taste and aroma also have effects.
- As cosmetics, essential oils cannot be substituted.
- So-called “green trends” also play a part in forming eating and medicating habits.
10. Preparation of home remedies
Infusion. An infusion is made from those plant parts that can be well impregnated by water and the active ingredient is water soluble. 15-30 g of the dried drug is necessary for about 0.5 litre of water, or 1-1.5 tablespoons of dried drug per cup. The flower, leaf or stem drug should be put in boiling water, then taken from the fire and let soaked for 10-20 minutes. If soaking time is longer, the tea will be stronger. Certain manuals suggest that when preparing an infusion, we put the dried (sometimes fresh) plant parts in a cup and pour boiling water over them. When using fresh parts, amounts should be doubled. Soaking may last for a few minutes or as long as 10-20 minutes, when the tea is strained. Sometimes it is enough to put the medicinal plant parts on a filter and pour boiling water over it. It is better to cover the pot during soaking because essential oils may evaporate but precipitating on the lid, they flow back into the infusion. While the tea cools down, inhaling the warm vapours is also medicinal.
Infusions often have an unpleasant or bitter taste. We can use sweeteners to enhance their aroma but it is often recommended we rather not. Nature seems to regulate overconsumption of certain substances by precisely the bitter taste. If a recipe mentions fresh infusion, it does not mean plant parts should be used fresh, but that the infusion should be taken fresh.
Decoction . It is similar to infusion, but we should let the decoction simmer for 10-20 minutes on low heat, especially root, fruit, bud and bark drugs, sometimes even stem and thicker leaf drugs. This stronger method is applied to extract materials less soluble in water, e. g., the root of dandelion. Evaporated water can be refilled after filtering.
Soaking. Due to ingredients sensitive to heat, certain plant parts may have to be soaked in cold or lukewarm water for at least 6-8 hours, or often longer, e. g., in the cases of marsh mallow, dog rose and mistletoe. As a general rule, one tablespoonful of drug should be added to 0.3 litre of water, and for poultices and washes, two-three times as much.
Bath. It is prepared by using pine and oak bark, oat straw, horsetail and mayweed.
Tincture. It is the alcoholic extract of the plant; it is more quintessential, so it can be transported or stored for longer. The drug should be soaked in alcohol at 10-30 °C for 6-8 days. The mixture should be shaken well every few days to help extract important compounds. During soaking, the change of colour of the liquid is a natural process. The jar, made of brown glass if possible, should not be exposed to direct sunshine. Commercial tinctures are made with 96% alcohol, in home-made products 50% alcohol is common. When ready, the tincture should be stored in a cool place, out of reach of children, because even a smaller amount can be dangerous or even lethal due to the strength of the substance.
2.9.1. Test questions
(More then one answer may be correct)
18. How is it possible that a medicinal plant has proven carcinogenic effects and it is still used for therapeutic purposes? Which of the following statements are true?
a. A single active ingredient was tested, not the overall effect.
b. The plant drug was extremely overdosed in tests.
c. Side-effects were unnoticed because they occurred only in very rare cases.
d. If the drug is harmful when consumed as a tea, it still can be applied externally.
19. What kind of active ingredients are starch and inulin?
20. Which of the folowing active ingredients is not a cyanogene glycoside?
21. Find the matching pairs.
a. A sugar compound is bound to a non sugar (aglycon) compound, it is water-soluble.
b. If combined with nitrogenous acids, they form salts.
c. Steam distilled, nitrogen-free substances that are very poorly soluble in water.
A. essential oils B. glycosides C. alkaloids D. morphine E. menthol F. sinigrin
22. What is the role of active ingredients in the vegetable world? List their functions.
23. What happens if poppy is exposed to more intense light? Which one of the following statements is true?
a. morphine content increases
b. codeine production appears
c. tebain production is reduced
24. Of the following statements, which one is true, which one is false?
a. At higher temperatures, the morphine content of poppy increased.
b. Due to irrigation, the drug content of woolly foxglove increased.
c. In draught, the essential oil content of scented mayweed decreased.
d. If nutrients are rich in nitrogen, Solanum species grow more leaves, which is bad.
25. Related species of the following plants can also be collected. Which of the following statements are false?
a. The flower of all linden species is suitable for medicinal use.
b. Both hawthorn species have the same medicinal value.
c. Several St. John’s wort species can be collected.
d. Most of the horsetail species are poisonous.
e. False chamomile can be collected together with scented mayweed.
26. Medicinal plants should not be collected:
a. on fields
b. near busy roads
c. in areas where waste was disposed
d. after having been sprayed with pesticides, if the waiting time has not elapsed
27. When drying, which of the following you need the most of to get 1 kg of dry drug?
a. of the flowery stem
b. of the fruit
c. of the flower
28. Which of the following methods do not require boiling water?
29. When do you have to simmer plant parts for 10-20 minutes?
When preparing: a. a decoction b. an infusion.
30. The following plants have to be soaked in lukewarm water, except for one. Which one?
b. dog rose
c. St. John’s wort
d. marsh mallow
3. Part 2. The Description of Medicinal Plants
In this part, we give detailed descriptions of the most important medicinal plants in their taxonomic order. These are the same plants that are listed in the requirements for the subject “Medicinal Plants and Drugs”. Accordingly, we will describe 118 plants, although we may refer to slightly more since two or more related species may figure under the same number, as is the case with nettle, mallow, oak, etc. species.
General descriptions of families will be relatively short, containing only those traits that are necessary for identification and classification. When describing families, we will give only the initials of the scientific names of flower petals of the inflorescence in question, as follows: P (perigonium) for perianth (or perigone, the outer parts of a flower), K (kalyx) for calyx (the outer whorl of a flower consisting of sepals), C (corolla) for corolla (the inner whorl of the perianth, consisting of separate or fused petals), A (androeceum) for the aggregate of stamens, and G (gynoeceum) for the aggregate of carpels in a flower, or inflorescence. If certain flower parts are situated in two whorls, for example the stamens stand in a double whorl, then the numbers indicating the individual whorls are connected with the + sign, e. g., A 3+3. If the petals of a flower part are united, the number is put in brackets. For instance, C (5) indicates that the five petals of the corolla are united. Comfrey has bell-shaped united petals and in order to determine the number of petals in it we can count the segments of the corolla. The inferior (perigynous) or superior (hypoginous) position of the ovary is indicated with a lower or upper dash after G, a superior ovary thus being indicated by e. g., G 5, an inferior ovary by e. g., G 2 ¯.
Plant descriptions are illustrated with photos. Plant descriptions are fairly short, concentrating only on the most important traits necessary for identification. The most important ones are underlined. After this short description, we list the most common uses of the plants, in other words we specify the diseases or health problems for which they can be applied. In the descriptions of medicinal uses, I mostly relied on the litreature given in the bibliography, but occasionally completed them with my own experience and observations.
This textbook naturally cannot replace an identification manual and all the relevant scientific litreature at the same time, but certainly may help familiarizing ourselves with medicinal plants and gives a general basis for those wishing to deepen their knowledge and pursue further studies of medicinal plants and drugs.
The second part is an integrate chapter which can only artificially be divided into subchapters. If we discuss plants according to their taxonomic order, dividing the chapter into subchapters would result in great disproportions because certain families comprise only a couple of plants while others may have as many as 19. The two alternatives would have been to ignore taxonomic order and proceed according to families, or to proceed according to taxonomic order, discussing certain plants belonging to the same family under two different sections. We chose the latter alternative and divided the 118 plants into eight groups. Students thus study 15 plants on one occasion, which method already proved itself useful in practice and did not cause any problem.
3.1. 1. From Horsetail to Common agrimony
Equisetaceae– The Horstail family
The stems have nodes and internodes and their surface is jointed and ridged. The membranous leaves of horsetails grow in whorls around the nodes and are fused into sheaths. The stem itself is hollow and is either simple or has whorls of branches at the nodes; when present, these branches are identical to the main stem except being smaller and finer.
Horsetail species have three types. Type 1. There is a separate sterile stem and a fertile stem. The spores are borne under sporangiphores in strobili, cone-like structures at the tip of the brown, non-clorophyllous fertile stem, which drops off after the spores are shed, giving way to new, green stems. 1.Equisetum arvense (Field or common horsetail) belongs to this category. Its whorled branches are square (but I found quincangular – i.e., having five angles – branches as well), and their lowest internode is longer. See Pictures 1a, 1b.
Type 2. The fertile stem does not drop off after spore shedding but greens out and branches off, while the strobili drop off, as, for example, in wood horsetail (Equisetum sylvaticum).
Type 3. There is a green (clorophyllous) stem growing from the start. The black strobili appear at the tip of the stem or at the whorled branches. These species are generally poisonous. The whorled branches of marsh horsetail (Equisetum palustre) are quincangular (but specimens with six-angled branches could be found too). Giant Horsetail has very few whorled branches, usually situated on the lower or middle part of the stem. The lowest internode of the branches is much shorter than the sheath of the main stem, the teeth of leaf sheaths are tiny and often drop off.
Drug: the green stem with the whorled branches above the ground (Equiseti herba). 70-80 percent of the ashes are made up of silica acid. In the past it was used to scour (clean, polish) tin dishes, hence its variant name, scouring-rush. The drug should not contain more than 3 percent of the black rhizome. It is a most common plant in cultivated fields, making them a suitable place for collection.
The active ingredients of field horsetail are silica acid, saponins, bitter materials, aconite acid, oxalic acid, equisetonin (saponin), and thiaminase enzyme, which breaks down Vitamin B1.
- It is a diuretic and a renal purifier; equisetonin is beneficial for patients suffering from renal infections and effectively dilutes renal stones.
- It is a diaphoretic (it has perspiratory effects) and is recommended for arthritis, rheumatic problems and gout; it also enhances bone flexibility and prevents line deposits.
- The anti-inflammatory and haemostatic activity of horsetail helps decrease or stop bleeding.
Equisetum species are able to take up gold when it is in a water solution, and even small quantities of the metal can beneficially affect joints. They contain small quantities of nicotine and can therefore be tobacco substitutes. They have a high selenium content that may cause problems at labour. Equisetonin is also a nerve poison mainly causing symptoms in the nervous system. If it is consumed by grazing animals their milk may turn bluish and astringent.
Pinaceae, Abietaceae – the family of Pine species
They are mostly evergreen trees with subopposite or whorled branches, and alternately spirally arranged, linear (needle-shaped) leaves. They grow dispersed, alone, or in groups of 2-5. The female flowers are usually cone-shaped with sterile and fertile scales which are usually woody.