INTRODUCTION

Botanicals form the largest category of cosmeceutical additives found in the marketplace today. They are plant extracts from leaves, roots, fruits, berries, stems, twigs, barks, and flowers. Crushing, grinding, boiling, distilling, pressing, and drying can prepare the extracts. They can be easily added to cleansers, moisturizers, astringents, treatment creams, colored cosmetics, and face masks. Their popularity as cosmeceutical additives can be attributed to the fact that they are an unregulated category of ingredients that fit nicely into over-the-counter products. Botanical additives for topical application are considered safe by the United States Food and Drug Administration, thus allowing the products to be marketed without obtaining drug status or being restricted by monographed ingredients.

Historically, botanicals formed the basis of all medical treatments at the time European settlers were first coming to America. These Europeans learned that the American Indians had an extensive pharmacopeia, based on native plants, that was passed from generation to generation through the wisdom of the medicine man in each community. These plant concoctions were mastered by the settlers, transported back to England, and incorporated into some of the earliest books on medical treatment. When the new English settlers were learning about North American plant extracts, a large body of knowledge utilizing plants from the Orient was also being developed. The richness of plant material in the tropical Orient led to different plant extracts of great diversity that were used in Oriental medicine and religious practices. Today cosmetic formulators have access to plant materials worldwide for incorporation into cosmeceuticals.

BOTANICAL ADDITIVE MANUFACTURE

The popularity of botanicals is largely due to the aura of natural products. Products derived from plants are felt to be free of synthetic chemicals, somehow providing benefits above and beyond active agents that are created in a laboratory. It may come as a surprise to many that botanicals must undergo a significant amount of chemical processing prior to incorporation into a cosmeceutical and this processing greatly affects the biologic effect of the botanical on the skin surface. Box 11.1 summarizes some of these considerations, which are discussed next.

The most important factor contributing to the biologic activity of botanical cosmeceuticals is the source of the plant material. The chemical constituents of the leaves, berries, stems, roots, and flowers may be different, each containing over 200 different individual chemical constituents. Furthermore, the season in which the plant material was gathered may also greatly influence its composition. Certain actives are present only in the fall when the leaves are shedding while other actives are only present in early spring when immature leaves are present on the branches.

It is also important to consider the processing that a plant-derived material must undergo before it can be placed in a skin care product. Raw crushed leaves added to a moisturizer will not provide an esthetically pleasing result. Usually, the plant material is heated or processed to obtain essential oils or other distillates that can be easily added to a cosmetic formulation; however, heating may destroy some of the active chemicals providing skin benefits.

Lastly, the amount of the active in the botanical extract is important in determining efficacy. Sometimes the botanical active is added in small amounts providing more marketing benefit than skin benefit; however, many botanicals are only required in low concentrations to provide the desired effect. In an attempt to obtain some standardization of botanical fractions, many raw material manufacturers procure the actual plant materials and determine which fraction produces the desired effect. This fraction (e.g. a particular turpene) is analyzed carefully to isolate its chemical composition. Once the mass spectrophotometry is completed, a synthetic copy can be created. In some ways these synthetic copies are better since they eliminate some of the variability associated with plant materials grown in various environments at various times of year. It is also possible to concentrate the active agent. However, there are some that feel plant materials can never be accurately duplicated by organic chemistry.

BOTANICAL ADDITIVES

Botanical pharmacopeias contain thousands of plants with anecdotal purported skin benefits lacking scientific validation. It is not possible to cover all currently existing extracts in this text, yet there are some botanicals that are currently widely used in the cosmeceutical marketplace. These botanicals can be characterized as antioxidants, anti-inflammatories, and skin-soothing agents (Table 11.1).

Table 11.1 Botanical cosmeceutical categories

BOTANICAL ANTIOXIDANTS

There are many botanical antioxidants, since all plants must protect themselves from oxidation following UV exposure in the outdoor environment in which they grow. These protective mechanisms have evolved over many years, providing interesting chemicals for extraction and incorporation into cosmeceuticals. Antioxidant botanicals quench singlet oxygen and reactive oxygen species, such as superoxide anions, hydroxyl radicals, fatty peroxy radicals, and hydroperoxides. Most botanical antioxidants can be classified as flavonoids, carotenoids, and polyphenols. Flavonoids and polyphenols possess a polyphenolic structure accounting for their antioxidant effect while carotenoids are derivatives of vitamin A. The largest source of botanical antioxidants is foods, such as those listed in Table 11.2. These extracts can be used topically, as well as consumed. Other popular botanical antioxidants include soy, curcumin, silymarin, and pycnogenol (Table 11.3).

Table 11.2 Nutritionally derived botanical cosmeceutical antioxidants

Table 11.3 Botanical cosmeceutical antioxidant agents

• Soy (Fig. 11.1)

Soybeans are a rich source of antioxidant flavonoids, known as genistein and daidzein. These substances have also been classified as phytoestrogens, since they are plant derivatives with a chemical structure similar to human estrogen. Topical estrogens have been shown to function as cosmeceuticals by increasing skin thickness and promoting collagen synthesis. It is interesting to note that genistein increases collagen gene expression in cell culture; however, there are no published reports of this collagen-stimulating effect in topical human trials. Genistein is a popular cosmeceutical topically functioning as a potent antioxidant scavenging peroxyl radicals and protecting against lipid peroxidation in vivo.

Fig. 11.1 Soybeans

• Curcumin (Fig. 11.2)

Curcumin is a polyphenol antioxidant derived from the turmeric root. Turmeric is a popular natural yellow food coloring sometimes used to color cosmeceuticals claiming to be free of artificial ingredients. Curcumin is consumed orally as an Asian spice, frequently found in rice dishes to color the otherwise white rice yellow. However, this yellow color is sometimes undesirable in cosmetic preparations, since yellowing of products is typically associated with oxidative spoilage. Tetrahydrocurcumin, a hydrogenated form of curcumin, is off-white in color and can be added to skin care products not only to function as a skin antioxidant, but also to prevent the lipids in the moisturizer from becoming rancid. The antioxidant effect of tetrahydrocurcumin is said to be greater than vitamin E by cosmetic chemists. Resveratrol, a chemical related to curcumin, is found in red wine, accounting for the antioxidant effect of this beverage. Thus, curcumin is a multifunctional ingredient providing cosmeceutical antioxidant benefits and also functioning as an antioxidant preservative.

Fig. 11.2 Curcumin

BOTANICAL ANTI-INFLAMMATORIES

Botanical anti-inflammatory additives are used in many different cosmeceuticals, since aging is in part the end result of chronic inflammation. Commonly used botanical anti-inflammatories include Ginkgo biloba and green tea (Table 11.4).

Table 11.4 Botanical cosmeceutical anti-inflammatory agents

• Ginkgo biloba (Fig. 11.3)

Ginkgo biloba is a plant with numerous purported benefits that is a common part of homeopathic medicine in the Orient. The plant leaves are said to contain unique polyphenols such as terpenoids (ginkgolides, bilobalides), flavonoids, and flavonol glycosides that have anti-inflammatory effects. These anti-inflammatory effects have been linked to antiradical and antilipoperoxidant effects in experimental fibroblast models. Ginkgo flavonoid fractions containing quercetin, kaempferol, sciadopitysin, ginkgetin, and isoginkgetin have been demonstrated to induce human skin fibroblast proliferation in vitro. Increased collagen and extracellular fibronectin were also demonstrated by radioisotope assay. Various unknown Ginkgo fractions are added to skin moisturizers for antiaging benefits, even though no controlled trials exist regarding cutaneous benefits.

Fig. 11.3 Ginkgo biloba

• Green tea (Fig. 11.4)

Green tea is a botanical popular in the Orient for both topical application and oral ingestion. Orally, green tea is said to contain beneficial flavonoids that act as potent endogenous antioxidants. A study by Katiyar et al demonstrated the anti-inflammatory effect of topical green tea application with C3H mice. A topically applied green tea extract containing the polyphenol epigallocatechin-3-gallate was found to reduce UVB-induced inflammation. This has been validated by measuring skinfold thickness before and after UVB exposure, which correlates with tissue edema, a sign of inflammation. Even though this is the cosmeceutical industry standard for assessing inflammation, it is a difficult test to replicate and may not directly correlate with a human response. At present, green tea remains a nutritional supplement and not an approved sun protective agent.

Fig. 11.4 Green tea

BOTANICAL SKIN-SOOTHING AGENTS

Botanical cosmeceuticals can also be used for the purpose of skin soothing. While this is a somewhat nebulous term, skin-soothing agents claim to calm, normalize, replenish, or relax the skin. Botanicals with these properties include prickly pear, aloe vera, allantoin, witch hazel, and papaya (Table 11.5). These plants have been selected for discussion due to their current novelty and popularity.

Table 11.5 Botanical cosmeceutical skin-soothing agents

• Prickly pear (Fig. 11.5)

Prickly pear, a plant native to the southwestern desert, is also known as cactus pear, Indian pear, or tuna fig. It was imported to Europe in the sixteenth century and became a part of a salve designed to soothe cutaneous wounds and burns. The fleshy pad of the prickly pear contains 83% water and 10% sucrose with small amounts of tartaric acid, citric acid, and other mucopolysaccharides. American Indians would rub the mucilage from the broken pad over the skin surface to act as a sunscreen and moisturizer.

Fig. 11.5 Prickly pear

Mucilages in general have a soothing, cooling effect on the skin, due to evaporation of water, when the plant juice is rubbed over the skin. Additionally, the mucopolysaccharides dry to form a protective coating over wounded or dermatitic skin. An extract of prickly pear is found in some moisturizer formulations. However, the extract is added as a dried powder and not as a mucilage which defeats the skin-soothing benefits for the most part. Nevertheless, prickly pear juice is found in a variety of skin care products.

• Aloe vera (Fig. 11.6)

Probably the most widely used botanical additive to soothe the skin is aloe vera. The mucilage is released from the plant leaves as a colorless gel and contains 99.5% water and a complex mixture of mucopolysaccharides, amino acids, hydroxy quinone glycosides, and minerals. Compounds isolated from aloe vera juice include aloin, aloe emodin, aletinic acid, choline, and choline salicylate. The reported cutaneous effects of aloe vera include increased blood flow, reduced inflammation, decreased skin bacterial colonization, and enhanced wound healing.

Fig. 11.6 Aloe vera

In most skin preparations, aloe vera is added as a powder, not as a mucilage. The composition of aloe vera powder may not be the same as aloe vera juice that oozes from the freshly broken plant leaf. Aloe vera extract is found in soaps, hair shampoos, hand lotions, body moisturizers, etc. It is estimated that aloe vera must be present at a concentration of 10% to have a moisturizing effect in products designed to remain on the skin for extended periods of time.

• Witch hazel (Fig. 11.7)

Witch hazel is a botanical extract most commonly used as an astringent in persons with oily skin. The plant was originally discovered by the Indians of the New England area of the United States. The extract is prepared by boiling the twigs and leaves of the plant, which grows as a low bush. The leaves can also be crushed and applied to the skin as a paste. The astringent action of witch hazel is probably due to the high tannin content of the plant.

Fig. 11.7 Witch hazel

Many cosmeceutical vein treatments contain witch hazel extract, since the tannins of the plant function as venous vasoconstrictors. Whether vasoconstriction can be achieved through topical application remains unknown. Witch hazel ointments, known as Hamamelis ointments, are used as acne cosmeceuticals.

• Papaya (Fig. 11.8)

Latex from the unripened fruit of the papaya plant, also known as the paw paw plant, is rich in papain. Papain is a proteolytic enzyme that is used in cosmeceutical wound healing and scar creams. It is also present in creams designed to speed the resolution of bruises.

Fig. 11.8 Papaya

SUMMARY

Botanical cosmeceuticals provide endless opportunities to add new marketing interest to traditional cleansers and moisturizers. Some botanicals actually contain substances that may provide skin benefits, while others are of questionable value. It is the knowledge base of the dermatologist that will ultimately determine those which are of patient value.