Type 1 diabetes is insulin dependent and type 2 diabetes is non-insulin dependent. About 90% of people suffer from type 2 diabetes. Although, with insulin injection, type 1 diabetes is treatable, finding drugs to treat and manage type 2 diabetes is an important area of research. Pancreatic α-amylase and intestinal α-glucosidase are key enzymes that convert carbohydrates to monosaccharides. Therefore, they are responsible for elevation blood sugar; and inhibiting these enzymes is an appropriate way to treat diabetes [
11]. The α-amylase enzyme has three domains (A, B, C) and has 496 amino acids. The catalytic site of α-amylase (PA) contains Asp197-Glu223-Asp300 amino acids [
12].
Salvia has been so popular that it has been the subject of numerous chemical studies. These plants are rich in polyphenols and contain more than 160 polyphenols, some of which are unique to the genus
Salvia. Several phenolic acetophenone glycosides have only been identified in
S.officinalis [
13]. There is a strong correlation between plant phenol content and inhibitory activities of α-amylase and α-glucosidase. Polyphenols are considered as potent antioxidants due to their redox properties in their hydroxyl groups [
14]. One of the important functions of polyphenols is to inhibit digestive enzymes, especially carbohydrate hydrolyzing enzymes such as α-amylase and α-glucosidase. Inhibitors of enzymes capable of digestion carbohydrates decrease glucose absorption. Polyphenolic α-amylase and α-glucosidase inhibitors derived from natural sources have been reported to be beneficial in reducing postprandial hyperglycemia [
15].
The results of this study showed that dichloromethane and methanol extracts of
S.mirzayanii inhibit α-amylase. In addition, according to Table
1, their mean IC
50 (IC
50 = 150.9 ± 6.7 μg / ml, IC
50 = 114.8 ± 11.1 μg / ml) respectively,is higher than the standard IC
50 acarbose (IC
50 = 42.9 ± 3.9 μg / ml). In other words, their levels of α-amylase inhibition were lower than acarbose. These results are consistent with the findings of a study by Dr. Moein et al. (2012) which showed that phenolic compounds in
S.mirzayanii may be responsible for free radical scavengingand the prevention of disease such as cancer and cardiovascular disease, diabetes and aging [
16]. It is also in line with Dr. Moein’s 2018 study, which showed that aqueous-methanol fractions of
S.mirzayanii inhibited the α-amylase, but further studies were needed to determine the type of inhibition [
17]. Study by Mohammad Reza Zarshenas in 2014 is consistent with the above mentioned results on diabetic model of rats, which showed that injection alcoholic extractof
S.mirzayanii decrease blood glucose levels [
18]. The results of this study also showed that dichloromethane (IC
50 = 71.2 ± 14.4 μg/ml, Table
1) and methanol (IC
50 = 54.9 ± 5.7 μg/ml, Table
1) extracts of
S.officinalis lower than acarbose (IC
50 = 42.9 ± 5.7 μg/ml). These results are consistent with the findings of Ahmad Ghorbani et al. (2016), who identified the phytochemical compounds of
S.officinalis flowers, leaves and stems. These compounds included alkaloids, carbohydrates, fatty acids, glycoside derivatives such as flavonoid glycosides, phenolic compounds and terpenoids that had anti-mutagenic, anti-inflammatory effects and anti-hypoglycemic activity and increased memory [
19]. More than 120 compounds have been characterized in the essential oil of aerial parts of
S. officinalis. The major components of this oil include borneol, camphor, caryophyllene, cineole, elemene, humulene, ledene, pinene, and thujone. Oxidative stress plays a significant role in the initiation and progression of several diseases, such as diabetes. The most effective antioxidant components of
S. officinalis are carnosol, rosmarinic acid, carnosic acid, caffeic acid, rosmanol, rosmadial, genkwanin, and cirsimaritin [
19]. It is also in line with studies by Rahman Mahdizadeh et al. (2018) who stated
S.officinalis reduces blood sugar levels in mice and inhibits gluconeogenesis and glycogenolysis in the liver [
20].
S. officinalis decreases blood glucose like acarbose, and also inhibits the activity of the intestinal maltase and sucrase and therefore possesses antidiabetic activity [
20]. These results are in line with the results of Eidey et al. (2009) who reported that methanolic extract of
S.officinalis significantly reduced blood glucose in hyperglycemic rats. In other study, ethanol extract of
S.officinalis leaves decreased blood glucose in rat diabetic model [
21].
The results of this study showed that dichloromethane (IC
50 = 100.9 ± 10.8 μg / ml, Table
1) and methanol (IC
50 = 103.7 ± 1.1 μg / ml, Table
1) extracts of
S.macilenta inhibited α-amylase, lower than acarbose (IC
50 = 42.9 ± 3.9 μg / ml, Table
1). Vasil Georgiev et al. (2017) reported that
S.macilenta is rich in phenolic acid and polyphenols, flavonoids and terpenoids. These compounds have hypoglycemic properties [
22]. It is also Mujtaba Asadullah’s reported that (2017) extracts of
S.macilenta and
S.officinalis are used in traditional Iranian medicine for treating many disorders such as diabetes [
23]. The results of this study showed that dichloromethane (IC
50 = 132.9 ± 15.88 μg / ml, Table
1) and methanol (IC
50 = 54.7 ± 9.6 μg / ml, Table
1) extracts of
S.santolinifola inhibited α-amylase, lower than acarbose (IC
50 = 42.9 ± 3.9 μg / ml, Table
1).