## 1 Introduction
### Antidiabetic and Anti-Obesity Properties
#### 1.2.1 Antidiabetic and Anti-Obesity Properties of Salvia Extracts--In Vitro methods  
Several authors reported the high capacity of distinct methanolic extracts, or of aqueous extracts, from _Salvia_ species, in inhibiting \(\alpha\)-glucosidase activity, including that of _S. officinalis, Salvia acetabulosa, S. nemorosa, S. sviraca, Salvia chloroleuca, S. elegans, S. cadmica, S. africana-lutea, S. aurita, S. blepharochlaena, S. euphratica var. leiocalycina and S.verticillata subsp. amasiaca_ [27; 51; 53; 58; 63; 64; 87; 88; 89], which in some cases were even more effective than the antidiabetic pharmaceutical drug acarbose (Table 3). In these studies, the authors have essentially correlated this ability with the phenolic constituents of the extracts; e.g., a strong correlation (r = 0.995) was found for the contents of caffeic acid and of caffeic acid derivatives (ranging from 20.8 to 74.1 mg/g extract), in aqueous extracts of _S. officinalis, S. elegans_ and _S. greggii_, and \(\alpha\)-glucosidase inhibition [27]. Likewise, when describing the high inhibitory capacity of aqueous and methanolic extracts of _S. cadmica_ (both rich in rosmarinic acid, luteolin and apigenin) towards \(\alpha\)-glucosidase and \(\alpha\)-amylase, [PERSON] and cowokers underlined a strong correlation between the \(\alpha\)-glucosidase inhibitory capacity with TPC (r = 0.986) and TPC (r = 0.917) [53]. In addition, in the study of [PERSON] et al. [58], the authors associated the strong \(\alpha\)-glucosidase inhibitory capacity of the methanolic extract of _S. nemorosa_ with its richness in phenolic and flavonoid compounds, namely rosmarinic acid, quercetin and caffeic acid (0.11 to 7.6 mg/g extract). The ability of sage phenolic compounds in acting as inhibitory agents of \(\alpha\)-glucosidase has in fact been proved by distinct researchers; e.g., isosalvianolic acid C methyl ester, rosmarinic acid methyl ester and salvianic acid A and C methyl ester, isolated from _Salvia milliorrhiza_, were reported to be stronger inhibitors of \(\alpha\)-glucosidase than acarbose [90]. Likewise, the flavonoids luteolin-7-O-glucose, luteolin-7-O-glucuronide and diosmetin-7-O-glucuronide, obtained from the aerial parts of _S. chloroleuca_, were also shown to exert \(\alpha\)-glucosidase inhibitory effects close to that of acarbose (IC\({}_{50}\) of 18.3, 14.7, and 17.1 uM, respectively, vs 16.1 uM) [89]. In addition to caffeic acid derivatives and flavonoids, some authors also underlined the efficacy of phenolic terpenids from sage origin to inhibit \(\alpha\)-glucosidase and/or \(\alpha\)-amylase [63; 64]. In particular, 7-methoxyrosmanol and rosmanol purified from _S. aurita_, were reported to be potent \(\alpha\)-glucosidase inhibitory agents (IC\({}_{50}\) of 4.2 and 16.4 ug/mL, respectively), while 12-methoxycarnosic acid and carnosol actively inhibited \(\alpha\)-amylase (IC\({}_{50}\) of 16.2 and 19.8 ug/mL, respectively) [64]. Note that phenolic dicterpenic compounds have been also claimed to act as antidiabetic agents by several other mechanisms, such as by reversing insulin resistance, modulating mediators of the insulin signaling pathway, promoting glycogen synthesis, inhibiting glycogen degradation, decreasing free fatty acids, inhibition of gluconeogenesis and decreasing blood glucose levels [82; 83]. Moreover, non-phenolic compounds, namely terpenids, have been also claimed as potential agents for the control of metabolic enzymes. In the study of [PERSON] et al. [63], ursolic acid and \(\beta\)-amyrin isolated from a methanolic extract of _S. africana-lutea_, were shown to be strong inhibitors of \(\alpha\)-glucosidase (IC\({}_{50}\) values of 11.3 and 17.1 ug/mL, respectively). Additionally, oleanolic acid purified from the same source displayed both high \(\alpha\)-glucosidase and \(\alpha\)-amylase inhibitory activity (IC\({}_{50}\) of 22.9 and 12.5 ug/mL, respectively) [63]. Although less investigated, the ability of polar _Salvia_ extracts to inhibit lipase was previously reported. In particular, methanolic extracts obtained from _S.