# Cosmeceutical Potentials of _Equisetum debile_ Roxb. ex Vaucher Extracts
## 1 Introduction  
Skin hyperpigmentation, wrinkles, and hair loss are not life-threatening conditions but are serious concerns leading to higher risks of social pressure, low self-esteem, and depression [1, 2]. Tyrosine, collagenases, and 5\(\alpha\)-reductase are the most studied enzymes for potential remedies of skin and hair problems. The reactive oxygen species (ROS) induced by ultraviolet (UV) radiation can cause skin hyperpigmentation disorders and photoaging by oxidative damage of skin lipids, proteins, and DNA and setting off enzymatic cascades relating to tyrosinase and collagenases [3]. UV radiation is also the most significant risk factor for nonmelanoma and melanoma skin cancers [4, 5, 6, 7]. Tyrosinase, a rate-limiting enzyme in melanogenesis, catalyzes a series of oxidations converting L-tyrosine to 3,4-dihydroxy-L-alanine (L-DOPA) and dopquinone. The polymerization of several dopaquinones then gives rise to melanin, causing skin to darken [6; 8]. Melanin normally protects skin from UV radiation via shielding effects. It serves as a physical barrier scattering UV and an absorbent filter reducing UV penetration through the epidermis [9]. However, when tyrosinase is overactivated by UV-induced ROS, it causes unpleasant skin hyperpigmentation disorders such as pigmented acne scars, senile lentigo, melasma, and freckles [10; 11]. Collagenases are key enzymes attributed to collagen degradation, which results in impaired skin structural integrity. Collagen is the main structural protein in the extracellular matrix constituting not only skin but also cartilage, bone, and other connective tissue. It is also involved in a wound-healing process by contributing to cellular migration and new tissue development [12]. Collagenases are zinc-containing proteinases that are a type of matrix metalloproteinases (MMPs). MMP-1 can trigger the breakdown of type I, II and III collagens, which are found abundantly in the dermis. On the other hand, MMP-2 is responsible for the degeneration of not only collagen type I-III but also type IV and VII, which mostly reside in the dermal-epidermal junction [13]. UV-induced ROS can increase collagenase activities via the MAPK pathway [5; 7]. When the ROS chronically and cumulatively induce the activities of collagenases, skin collagens can become depleted over time, leading to wrinkle formation, aging skin, and delay of wound healing [14]. In addition to healthy skin, hair is another aesthetic concern for overall appearance. Androgenic alopecia (AGA) is the most common hair loss affecting both men and women. Early onset appears in the teens; however, most cases occur later in life. It affects 50% of males by age 50 years and up to 70% by 70 years [15; 16]. AGA is a genetic disorder of dysfunctional androgens caused by the inordinate induction of 5\(\alpha\)-reductase in hair follicles [17]. This results in an acceleration of excessively converting testosterone to the higher potent dihydrotestosterone, which then trigger the development of AGA pathogenesis leading to hair loss and pattern baldness [18; 19]. Nowadays, treatments addressing skin hyperpigmentation, wrinkles, and hair loss mostly involve chemically synthetic compounds that often lead to undesired effects. Tyrosine inhibitor hydroquinone is a depigmenting agent used to lighten darkened skin; however, it causes dermatitis, edema, and ochronotic condition [20]. Skin aging remedies involving topical hydroxyl acid to shed old sun-damaged epidermal layers, topical retinoids to improve fine lines, and directly injecting collagen to reduce wrinkles can lead to hyperpigmentation, inflammation, and bacterial infection [21; 22]. For hair loss, potassium channel opener minoralid and 5\(\alpha\)-reductase inhibitor finasteride are the only two drugs that are currently approved by the United States Food and Drug Administration (US FDA) for AGA [2]. However, minoralid causes erythema, dizziness, and tachycardia, while finasteride leads to erectile dysfunction, gynecomastia, and severe myopathy.