Menopause is a period of women's life, which often occurs at the age of 51 years. According to the World Health Organization (WHO), the population of menopausal women will reach 1.2 billion in the world by 2030 [1]. Women spend one-third of their life in the post-menopausal period [2]. Approximately 75% of these women experience vasomotor symptoms (VMS), such as hot flashes and night sweats. In fact, VMS hot flashes are among the most common and disruptive symptoms in menopausal women [3]. Hot flashes adversely affect professional and social activities, leisure time, temperament, concentration, communication, sexual activity, enjoyment of life, and quality of life [4]. In menopausal women, hormonal therapy is considered to be the main medical treatment for hot flashes and night sweats although contradictory results have been proposed in this regard. For instance, some studies have demonstrated the possible risks associated with hormone therapy, such as endometrial and breast cancer and the increased risk of thrombophlebitis, cardiovascular disorders, and myocardial infarction. On the other hand, some findings have denoted benefits such as the reduced risk of endometrial cancer and bone fractures [5]. Therefore, hormone therapy is not recommended to some women, while others may be benefitted [6].

Women are increasingly seeking complementary and alternative treatments to alleviate menopausal symptoms [7]. Recently, medicinal plants have attracted the attention of researchers, and the use of herbal products has been on the rise across the world. According to the studies by the WHO, 80% of the world’s population is encouraged to use herbal medicines for various purposes [8]. Herbal medicines have been historically used and are widely accepted by the community [9].

Viola odorata has long been used in the Iranian traditional medicine. According to traditional medicine specialists, V. odorata has a cold and humid temperament, and all its parts have therapeutic properties [9]. The flowers and leaves of V. odorata contain methyl salicylate, beta-nitropropionic acid, flavonoids, saponins, mucilage, alkaloid, vitamin C, magnesium, polin, and melatonin [10]. Plants with phytoestrogens are preferred over the other options in the herbal treatments for hot flashes and night sweats [11].

Since phytoestrogens are structurally similar to 17 beta-estradiol, they affect the body in a similar manner to estrogen [12]. Lignans and flavonoids are two phytoestrogens that have been extensively studied. V. odorata is an abundant source of flavonoids (22.8 mg/g) [13], which are polyphenolic compounds with similar properties to estrogen and are obtained via the pathway of phenylpropanoid metabolism [14]. Notably, estrogen deficiancy is known as a major cause of hot flashes and night sweats during menapuase [2]. Several studies have indicated that herbal estrogens or phytoestrogens could be applied to reduce various menopausal symptoms, such as hot flashes and night sweats. In a research conducted by Salehi et al. (2013), red clover was used as an abudnant source of isoflavone, which is an important phytoestrogen, in order to alleviate menopausal symptoms. In addition, Golzareh et al. (2017) applied fennel to alleviate the physical symptoms of menapause through the flavonoid content of the plant.

Although some studies have been focused on hot flashes and night sweats in menopausal women, no research has evaluated the effects of the therapeutic use of V. odorata on menopausal hot flashes and night sweats. In addition to imposing an economic burden on families and the community, hot flashes and night sweats are symptoms that reduce the quality of life of women during menopause, which is a period accounting for almost one-third of women's life and affects their life expectancy.

The present study aimed to assess the effects of V. odorata syrup on hot flashes and night sweats in menopausal women.