## 4 Conclusions  
_Salvia_ species were revealed as the best sources of CA, CS and 12 MCA among the studied species. It should be highlighted that _S. somalensis_ was identified as the richest source of CA and CS and _S. microphyllla_ as the richest source of 12 MCA. Moreover, \({}^{1}\)H-qNMR spectroscopy offers a useful tool for the quantitative and qualitative analysis of the examined compounds in complex extracts, in a simple, rapid and direct way, with high precision and without sample deterioration. This aligns with previous findings, where quantitative NMR (\({}^{1}\)H-qNMR) has proven highly effective for the determination of the bioactive metabolites content in natural products [33]. It should be emphasized that the \({}^{1}\)H-qNMR methodology can be applied in extract standardization and quality control in herbal medicines. The main limitation of this study is that the majority of the studied samples came from a botanical garden and not from a real natural ecosystem, and for this reason, it cannot be excluded that environmental factors related to the natural ecosystems could lead to different levels of the studied compounds. However, the fact that the majority of the plant samples were cultivated under the same conditions reduces the impact of environmental factors, and consequently, the obtained results regarding the levels of the studied metabolites are mainly influenced by genetic factors related to each studied species. Another limitation is that only a small number of individual plants of each species were studied, and for this reason, we cannot exclude the possibility of variation in the levels of the studied compounds among individual plants of the same species. Furthermore, we cannot exclude the possibility of annual variation since we collected plants from only one year. A secondary limitation is that NMR has limited sensitivity in comparison to LCMS, so some plants that were identified as non-producing could actually produce very low amounts of the studied metabolites, lower than the limit of detection of the applied qNMR method. This limitation is not important for the identification of plants that could be used as source of the studied metabolites but could be important for chemotaxonomic studies, which are, however, outside of the scope of the current work. Based on the above, we propose future research focuses on studying the species that exhibit the highest levels of CA, CS, and 12 MCA in their natural habitats. This should include investigations into their geographical variations, as well as seasonal and annual variations, in order to determine the optimal conditions for abietane diterpene production. Figure 6: \({}^{1}\)H-NMR spectra of _Betonia officinalis_ L. (green color) and _Stachys officinalis_ (L.) Trevis (red color) in CDCl\({}_{3}\). **Supplementary Materials:** The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app15158361/s1](https://www.mdpi.com/article/10.3390/app15158361/s1)]([https://www.mdpi.com/article/10.3390/app15158361/s1](https://www.mdpi.com/article/10.3390/app15158361/s1)), Table S1: Plant species identifier codes; Table S2: Plant species showing no detectable levels of the tested metabolites; Table S3: The results for plants in the Labiatae family, analyzed both quantitatively and qualitatively, for the following compounds--carmosic acid (CA), carnosol (CS), and 12-methoxy-carmosic acid (12 MCA)--are presented as the mean \(\pm\) standard deviation (mg/g of dried leaves). 7-O-methyl-epi-rosmanol (7 MER) and rosamanol (RO) were not detected in any of the extracts; Table S4: Total of the abietane diterpenenes tested (RO, 7 MER, CA, CS, 12 MCA). Values are in mg/g of dried drug (d.d.) (sum of the averages of the individual substances). The last column shows the weight in mg of the dry methanolic extract resulting from 1 g of the drug in question; Figure S1: Degradation pathway of carnosic acid in methanol. **Author Contributions:** Conceptualization, P.M. and P.K.