**2. Anatomical and physiological changes in wound bed**

In mammals, wound healing is a rapid process involving cessation of bleeding from the wound, restoration of damaged tissues, moisture deposition around the wound to develop functional defense membrane which prevents microbial invasion. Thus, wound healing can be categorized into four stages which comprises of initial inflammatory phase, re-epithelialization, granulation tissue formation, and finally tissue remodeling [20]. This categorization is based upon histological examination or functional activities which are considerably overlapping. A deep interaction between cells and tissues involved in these phases finally results in wound healing [21].

Activated blood coagulation factors, complement components and damaged cells secrete growth factors and platelets which trigger chemotactic stimulus. Blood coagulation factors in conjunction with platelets initiate blood coagulation and activate fibrin. Fibronectin and vitronectin present in blood plasma form the substrate for cell migration involving keratinocytes. This is eventually followed by proteinases which result in scab formation around the wound [22].

As the blood coagulation process advances, within few hours neutrophils reach at the site of damaged tissue. They eliminate infective agents by phagocytizing them and promote blood coagulation and healing by secreting various factors [23]. Monocytes arrive at the wound within two days and differentiate into macrophages, to perform phagocytosis and antigen presenting functions. These macrophages regulate wound healing process by secreting, transforming growth factors-α and β, basic fibroblast growth factor, and platelet-derived growth factor [24]. Within few hours of inflammatory reaction, both re-epithelialization and granulation tissue formation takes place simultaneously. Keratinocytes present around the edges of the wound and in residues of skin appendages migrate into the wound and form a scab [25]. These keratinocytes are typically hyper-proliferative facilitating them to fill the damaged epithelial layer and reform the basement membrane within two days, restoring cellular contacts. This process leads to differentiation of keratinocytes into epidermal skin layer [26]. At almost the same time fibroblasts located around the undamaged dermis begin to proliferate and migrate as a result of the stimulus caused by the aforementioned growth factors, granulation tissue formation [27]. The extracellular around the wound is formed by proteoglycans, collagen type I and III, and collagen secreted by fibroblasts [22]. A portion of fibroblasts differentiate into myofibroblasts, which secrete actin, which builds up mechanical tension brings the edges of the wound closer resulting in wound contraction and finally wound closure [26]. The migration and proliferation of endothelial cells result in appearance of new blood vessels in granulation tissue [24]. The dermis remodeling phase of skin wound healing involves reduction of fibroblasts by apoptosis and removal of damaged blood vessels. The residual fibroblasts rearrange the collagen fiber, repeating collagen deposition and degradation for several months in order to recover the original tension of the skin [27].

Radicals produced by wounds are largely superoxide radical anions produced by neutrophils and macrophages, and also play an important role in removal of microorganisms and pathogens [28]. Superoxide radical anions are quickly transformed into hydrogen peroxide (H2O2) which is able to permeate microorganisms or pathogenic cell membranes by superoxide dismutase, promoting the formation of hypochlorous acid, chloramines, and aldehyde which are all maintained in more stable forms than H2O2, and are characterized by long half-lives. Thus, if H2O2 remain in the wound for extended period of time, acute inflammatory reactions can damage even normal cells [29].

Saponins present in various plant extracts possess extensive biological activities. They augment anti-oxidants and anti-inflammatory reactions. Saponins are one of several kinds of glycosides present in plants of high order [30]. Saponin types are named based upon their internal structure. A saponin referred to as fruticesaponin B is known to have a very high anti-inflammatory activity [31]. Navarro et al. [32] reported that anti-inflammatory activity of saponins is highly dependent on their chemical structure. In fact, both types of saponins tested in the study, prevented neutrophil access to wounds thereby decreasing chronic skin inflammatory reactions. On day 5, the wound healing rate was much faster in saponin-treated group than the control leading to complete joining of both sides of the incisional wounds on day 7. Except for day 1, during all time periods of evaluation, the wound area contracted more in the saponin-treated group than the control group. However, except day 1, the rate of keratin cell migration in the saponin-treated group was found to be higher than the control group during all periods. Another study reported that the burn wound area in a saponin-treated group was found to gradually increase up to day 4 then gradually decrease until day 20. In control group, the burn wound area gradually increased up to day 8 and then diminished in size [33]. The long lead time in healing the burn wound was due to inflammatory reaction around the burn wound which persisted longer [34]. Saponins were found to stimulate overexpression of factors, leading to proliferation of epidermal cells [35]. It was also found that rate of keratinocytes migration involved in re-epithelialization was faster in the saponin-treated group than in the control group. Hence, it was concluded that saponin not only enhances epidermal cell proliferation but also promotes migration of keratinocytes. The influx of inflammatory cells was measured in an animal wound model. On day 1 and day 3 it was found that the number of inflammatory cells in the saponin-treated group were much less in comparison to the control group. But were found to increase from day 5.

*Anti-Inflammatory Potential of Ginseng for Wound Healing DOI: http://dx.doi.org/10.5772/intechopen.101167*

On day 7, the number of inflammatory cells were greater in the treated group than the control group. In burn wound number of leukocytes and macrophages increased up to day 9 [19]. Accumulation of macrophages was induced by IL-1β expression by hypoxia-inducible factor-1α. Hence, it is quite obvious that saponins are involved in inhibition of the inflammatory reaction at an early stage. Moreover, wound shrinkage increased sharply from day 3 onwards as compared to control group. Matrix remodeling analysis confirmed that matrix synthesis was promoted in the saponin-treated group compared to the control group. A recent study revealed that when saponin are used to treat skin tissue exposed to ultraviolet rays, collagen synthesis of fibroblasts was increased and expression of matrix metalloproteinases was inhibited [36]. It was also found that saponins increased collagen synthesis through phosphorylation of Smad 2 protein. Hence, saponins promote the regeneration of matrix at the wound site [37].

Hence, the literature findings very well indicate that saponins stimulates re-epithelialization of the wound and effectively inhibit early phase inflammatory reactions during and promotes matrix synthesis throughout the wound healing process. On the basis of the evidence existing in literature saponins are beneficial in healing incisional skin wounds. Ginseng leaves can be easily acquired and much cost effective compared to ginseng roots, hence there are several reports on isolation of active compounds from the Chinese ginseng leaves. These novel compounds were also tested for wound-healing activity [15].
