# Cosmeceutical Potentials of _Equisetum debile_ Roxb. ex Vaucher Extracts
## 1 Introduction
Therefore, there are rising demands for natural products as alternatives to chemically synthetic ingredients in skin and hair treatments. In addition, increasing awareness of the harmful impacts of synthetic chemicals on the environment is another attribute accelerating the growth of incorporating natural elements in cosmeceuticals. Horsetails (_Equisetum_) are one of the oldest vascular plants that have existed prior to the continental drift as indicated by fossil records. _Equisetum_ comprises over thirty species, and due to the adaptability to distinct climates, their distribution spans from the equator to the northern hemisphere [23; 24]. Horsetails are also known as the most ancient remedies in several countries. _E. arvense_ L., native to north America and Europe, is the most investigated horsetail due to the long-standing traditional usage. Its medicinal values, particularly for skin and hair care, have been recorded not only in folklores but also in scientific literature. Traditionally, it is used to treat poorly healing wounds, hair loss, brittle nails, bone fractures, diuretic, and rheumatic diseases, potentially due to the species' high silica, total phenolics, flavonoids, phytosterols, and saponins [23; 25; 26]. In cosmeceuticals, _E. arvense_ extracts are recognized as a skin collagen-promoting agent,anti-aging agent, and hair-promoting ingredient. Mixtures of _E. aureus_ extracts with other herbs in dietary supplements and topical formulations are known to promote healthy hair follicles and hair growth. A placebo-controlled, single-blind, clinical instrumental study showed that herbal formulations containing _E. aureus_ extracts helped prevent hair from falling out and reduced hair loss [27]. In clinical trials, topical phytotherapy combining _E. aureus_ extracts with other herbal extracts showed benefits to brittle nail disorder. Ointment containing _E. aureus_ (3%) showed wound-healing effects [28]. Other clinical trials reported the efficacies of _E. aureus_ for benign prostate hyperplasia and chronic musculoskeletal pain [29]. Additionally, the diuretic effect of _E. aureus_ was superior to control but equivalent to hydrochlorothiazzide [30]. On the other hand, _E. debile_ Roxb. Ex Vaucher, a species native to tropical Asia, is a far less studied horsetail [24]. In Thailand, it is distributed throughout the northern highland with typical hills up to 500 m. Traditionally, the local hill tribe people prepare decoctions of _E. debile_ for strengthening hair, treating urinary incontinence, kidney stones and backpain. Poultices of _E. debile_ are used for healing warts, wounds, bone fractures and joint pain. The similarity of morphological taxonomy, genetic relevance, and traditional usages between the two species suggest that _E. debile_ may possess comparative phytochemicals and pharmacological activities to _E. aureus_. _E. debile_ may possibly be a tropical counterpart to a temperate _E. aureus_ for the species' medicinal benefits. Horsetail-based commercial products are mostly derived from the _E. aureus_ due to not only being highly supported by scientific studies more often than other horsetail species but also being recognized and established as an herbal medicine in the monograph of European Pharmacopoeia 8 th edition [31]. Conversely, _E. debile_ is still underexploited despite potential medicinal values. _E. debile_ has been studied for total phenolic content, antioxidant activities, antibacterial activities, 5\(\alpha\)-reductase inhibition, interleukin 6 (IL-6) secretion inhibition, evaluation of membrane irritation, cytotoxicity, and phytochemical isolations of pinochemrin, chrysin, \(\beta\)-sitosterol, flavonoid glycoside, fatty acids, and megastigmane diglucoside [32; 33; 34]. However, previous reports were limited to the investigation of extracts obtained from macrozations. Horsetail plants are known to accumulate considerable amounts of silicon (Si) [35]. Si is found in various tissues of the human body and present in 1-10 parts per million in hair and nails [36].