## 3 Results and Discussion
The chemical structures of the studied abietane dieterpenes (Figure 1) show high similarity; however, due to specific structural differences, each compound presents different chemical shifts in the \({}^{1}\)H-NMR spectrum when recorded in CDCl\({}_{3}\) (Figure 2). Note that the abietane C ring in all the cases of CA, CS, 7 MER, RO and 12 MCA is aromatic and the characteristic peaks that were used for identification and quantitation appear in the region between 6.56 and 6.86 ppm. The structural assignment of each compound was confirmed by comparing the \({}^{1}\)H-NMR spectra (recorded in CDCl\({}_{3}\)) of the purified compounds with those obtained from the crude plant extracts. This comparative analysis allowed the reliable identification of the abietane dieterpenes, consistent with previous studies. In all the plant extracts that were analyzed, there was no case in which CS or 12 MCA was identified without the presence of carnosic acid (CA). This is probably due to the fact that CS results from the conversion of carnosic acid and cannot be identified without the presence of the latter. This observation, in terms of CS and CA, is in full agreement with the work of [PERSON] et al. (2008) [14], who investigated methanolic extracts, by HPLC/MS, in 60 species of the genus _Salvia_ in terms of CS, CA, 12 MCA and isorosmanol, finding that all the CS-containing plant species also had CA in their leaves, but not the other way around. Indeed, CA has been shown to be the precursor of phenolic dieterpenes with \(\gamma\)- and \(\delta\)-lactone structures and, in the presence of oxygen, CA is converted into CS and isorosmanol [15; 16]. **Plants that did not contain any of the studied metabolites**  
Analysis of the \({}^{1}\)H-NMR spectra showed that the following plants did not contain any of the studied metabolites: _S. superba, S. bucharica, S. desoleana, S. transylvanica, Phlomis cretica, Phlomis fruticosa, Mentha pulegium L., Sideritis clandestina [PERSON], Hysogus officinalis L., Satureja thumbra L., Betonica officinalis L., Nepeta cataria L., t Marrubium vulgare L., Satureja juliana L., Stachys chrysantha [PERSON]. & [PERSON], Stachys iva Griseb, Teucrium capitatum L., Teucrium flavour L., Laminium album L., Laminium garganicum L., Ballota acetablusosa L., Nepeta melissifolia Lam., Stachys officinalis (L.) Trevis, Origanum vulgare subsp. _[PERSON]_ (Link), Origanum majorana L., Origanum dictamus L., Thumbra capitata (L.) Cav., S. _cadmica_ [PERSON], _S. ringens_ [PERSON], _S. chionantha_ [PERSON], S. _S. sclarea_ turkestanica ([PERSON]) [PERSON], _S. sclarea_ L., S. scabiosifolia Lam., S. misella [PERSON], _S. dominica_ L., S. leucantha_ Cav., _S. recognita_ [PERSON]. & [PERSON], _S. viscosa_ [PERSON]. The \({}^{1}\)H-NMR spectral qualitative analysis of the methanolic extract of _S. sclarea_ L. showed that none of the abietane diterpenes could be identified. This result does not agree with the work of [PERSON] et al. (2017) [17], who detected CA (\(\sim\)195 \(\upmu\)g dry weight) in the ethanolic plant extract, and [PERSON] et al. (2019) [18], who also identified CA in _S. sclarea_ L. methanolic extracts from three different regions of Iran. The presence or absence of carnosol is not reported in the two studies mentioned above. The result for _S. sclarea_ L in the present study aligns with that of [PERSON] et al. (2008) [14], who also did not detect any abietane-type diterpene metabolites. The \({}^{1}\)H-NMR spectrum analysis of _Hysogus officinalis_ L. did not indicate the presence of any of the studied compounds. However, in the study by [PERSON] et al. (2010) [19], analysis of the CO\({}_{2}\) extract using the HPLC-DAD/ESI-ToF method revealed the presence of CS at a concentration of 7.3341 g/100 g of extract, while CA was absent. These findings differ from those of the present study, where CA was also consistently detected in every plant sample in which CS was present. None of the three species of the genus _Origanum_ (_O. vulgare_ subsp. _hirtum, O. majorana_ and _O.