3.3.1. Achyranthes aspera
This medicinal plant is traditionally used for the treatment of Acne vulgaris, eruptions of the skin, boils, scabies and other skin diseases. Saponin, alkaloid and non-alkaloid fractions obtained from the leaves of this plant have enormous inhibitory effect on the Epstein-Barr virus early antigen activation in Raji cells, with the most inhibitory activity (96.9%; 60% viability) observed for the non-alkaloid fraction, which contains non-polar compounds. In the in vivo two-stage mouse skin carcinogenesis test the total methanolic extract possessed a pronounced anti-carcinogenic effect (76%). The results revealed that the leaf extract and the non-alkaloid fractions were valuable antitumor promoters in carcinogenesis. The plant has abortificient properties in rodents and also has contraceptive activity, which might be due to its potent estrogenic activity (76).
3.3.2. Allium cepa
Onion extract gel has shown the ability to improve the appearance of scars in patients with seborrheic keratosis. This extract gel has been shown to improve the scar’s appearance by improving its redness, softness and texture at excision site four, 6 and 10 weeks after the extract usage (76). In another study, the antimicrobial and antifungal properties of a A. cepa and A. sativum were revealed against Malassezia furfur, Candida albicans and some other Candida sp, as well as some strains of dermatophytes and Acne vulgaris microbes. The results indicated that A. cepa and A. sativum might be promising in the treatment of bacterial and fungal-associated infections (77).
3.3.3. Azadirachta indica
In a study, conducted on an anti-acne formulation prepared from herbal extracts, it was revealed that ethanol extract of Azadirachta indica, G. glabra, Andrographis paniculata, Ocimum sanctum, and green tea possessed the potential for inhibiting acne. In this study the anti-acne formula successfully acted against Propionibacterium and Staphylococcus epidermis (78). Aqueous extract of Azadirachta indica leaves also possess chemopreventive potential against murine skin carcinogenesis. Skin tumors have been shown to enhance the expression of proliferating cell nuclear antigen in comparison to the control group. In this study, skin tumors exhibited high level of lipid peroxidation (40).
3.3.4. Cannabis sativus
The seed oil of Cannabis sativus is useful for the treatment of acne rosacea, seborrhoeic dermatitis, eczema, dermatitis, psoriasis and lichen planus. The leaves powder of this plant is very useful as a wound and sore dressing. Cannabis sativus extract is externally useful to relieve pain in itchy skin. The seed oil strengthens the skin and makes it more resistant to bacterial, fungal and viral infections (79).
3.3.5. Echinacea angustifolia and Echinacea purpurea
The extract of Echinacea purpurea has been shown to readily kill P. acnes, which is the main cause of acne vulgaris. In cell culture models, P. acnes induced substantial secretion of several pro-inflammatory cytokines, such as IL-6 and IL-8. However, the E. purpurea was able to completely reverse this effect to normal leaves. Hence, E. purpurea provided a safe two-fold benefit to acne patients by inhibiting bacterial-induced inflammation and inhibiting the proliferation of organism (49). Echinacea has also been used to treat other skin problems such as psoriasis, skin wounds, burns, ulcers, herpes and hemorrhoids (71).
3.3.6. Rosmarinus officinalis
Rosmarinus officinalis is a household plant, which is grown in many parts of the world. It is used as a beverage drink, flavoring food, as well as in cosmetics. Rosmarinus officinalis contains rosmarinic acid. Chronic UV exposure has manifestations such as photo-cancers and photo aging. Aqueous extract of R. officinalis is effective in prevention of photo damage induced by UV radiations due to its antioxidant effect (71). Infections are also associated with oxidative stress. Therefore, the compounds, which possess antioxidant properties, might be beneficial in this way, regardless of their antibacterial activity. Rosmarinus officinalis oil has also been effective against P. acnes, a type of bacteria that causes acne. In a study, the antibacterial properties of R. officinalis essential oil was evaluated against P. acnes in which significant changes were reported in size and morphology of P. acnes in response to treatment (80).
3.3.7. Melaleuca alternifolia
Melaleuca alternifolia or tea-tree is a tree or tall shrub in the plant genus Melaleuca. It is native in Australia, and occurs in north coast and adjacent areas of New South Wales. It also grows on swampy flats and along streams and where it occurs, it is often the dominant species. Tea tree oil is a broad-spectrum agent against Gram-positive and Gram-negative bacteria and even S. aureus resistant to methicillin and yeasts such as C. albicans in vitro. Its mechanism of action has been attributed to monoterpenes, which cause disruption of the plasma membrane barrier. Other than antimicrobial activity, tea tree oil has monocyte activators and anti-inflammatory activities. Topical use of low concentrations of tea tree oil has anti acne activity with low side effects. It is effective in chronic infectious wounds and osteomyelitis (81).
3.3.8. Eucalyptus globulus, E. viminalis and E. maculata
In one study, the leave extractions of 29 Eucalyptus species were examined for anti-microbial activities. Extractions of Eucalyptus globulus, E. maculata and E. viminalis were able to inhibit the growth of six gram-positive bacteria including P. acnes, S. aureus, Enterococcus faecalis, Bacillus cereus and Alicyclobacillus acidoterrestris, and a fungi, Trichophyton mentagrophytes, yet they did not show a strong inhibitory activity against gram-negative bacteria. A component of E. maculate (8-desmethyl-eucalyptin) also had strong inhibitory activity against the above-mentioned microorganisms. The authors concluded that Eucalyptus extracts and some components isolated from this plant had an inhibitory effect on microorganisms causing acne and Athlete’s foot infection, as well as some fungal infections (18). Clinical trials with positive effects are summarized in Table 1.
Clinical Trials With Positive Effects