This article provides a critical overview of current methods to quantify essential oil components. The fields of application and limits of the most popular approaches, in particular relative percentage abundance, normalized percentage abundance, concentration and true amount determination via calibration curves, are discussed in detail. A specific paragraph is dedicated to the correct use of the most widely used detectors and to analyte response factors. A set of applications for each approach is also included to illustrate the considerations.of linalool, linalyl acetate, β-pinene, sabinene, limonene and α-terpineol. 9 Figure 3 reports the enantioselective-gas chromatography-total ion mass spectrometry (ES-GC-SCAN-MS) profile of an adulterated bergamot EO together with those of linalool and linalyl acetate and α-terpineol in enantioselective-gas chromatographyselected ion monitoring mass spectrometry (ES-GC-SIM-MS) and their enantiomeric ratios.Normalized % abundance can be assumed to be a 'quantitative' comparison of GC profiles, but for some applications it is not sufficient to satisfy all quantitation Figure 3. ES-GC-TIC-MS profile of bergamot EO. (A) Peak identification: 1, α-pinene; 2, β-pinene; 3, sabinene; 4, limonene; 5, linalool; 6, linalyl acetate; 7, α-terpineol; a, (R) enantiomer; b, (S) enantiomer. ES-GC-SIM-MS profiles and enantiomeric ratios of (B) linalool and linalyl acetate (80, 93, 121 m/z) and (C) α-terpineol (59, 93, 136 m/z). Analysis conditions: column, heptakis-2,3-di-O-ethyl-6-O-t-butyldimethylsilyl-β-CD, 30% in PS086 (Megadex, Mega ® ), 25 m × 0.25 mm i.d., 0.25 μm film thickness; temperature programme, 50°C, rising at 2°C/min to 200°C, then held for 5 min; injection mode, split (ratio 1:50); injector temperature, 220°C; EI mode, 70 eV; ion source temperature, 230°C; carrier, helium; flow rate, 1.0 ml/min in constant flow mode. Full scan mode: scan range, 35-350 m/z; SIM mode: dwell time, 0.2 sFigure 4. GC profile of peppermint EO. Analysis conditions: Megawax (60 m × 0.25 mm i.d., 0.25 μm film thickness); temperature programme, 75°C for 8 min, rising at 4°C/min to 220°C, then held for 5 min; injection mode, split (ratio 1:100); injector temperature, 230°C; detector (FID) temperature, 250°C; carrier, H 2 ; flow rate, 1.5 ml/min in constant flow mode

Artemisia umbelliformis Lam., an important alpine plant used for the preparation of flavored beverages, showed a remarkable intraspecific variability, at both genomic and gene product (secondary metabolites) levels. The variability of A. umbelliformis Lam. currently cultivated in Piedmont (Italy, Au1) and in Switzerland (Au2) was investigated by combining the chemical analysis of essential oil and sesquiterpene lactones and the molecular characterization of the 5S-rRNA-NTS gene by PCR and PCR-RFLP. Marked differences were observed between the two plants. Au1 essential oil contained alpha- and beta-thujones as the main components, whereas Au2 contained 1,8-cineole, borneol, and beta-pinene. Au1 sesquiterpene lactone fractions contained cis-8-eudesmanolide derivatives and Au2 the trans-6-germacranolide costunolide. Specific A. umbelliformis Au1 and Au2 primers were designed on the sequence of the 5S-rRNA gene spacer region. Furthermore, a PCR-restriction fragment length polymorphism (PCR-RFLP) method was applied using RsaI and TaqI restriction enzymes. Chemical and biomolecular data contributed to the characterization of A. umbeliformis chemotypes.

Giant fennel (Ferula communis L.) from Sardinia is characterized by two chemotypes with different biological activities. One chemotype is poisonous, due to prenylcoumarins, and responsible for ferulosis, which mainly affects sheep and goats, cattle, and horses; the other chemotype is nonpoisonous and contains daucane esters. The two chemotypes cannot be distinguished botanically. High-performance liquid chromatography-diode array-ultraviolet detection-mass spectrometry (HPLC-DAD-UV-MS) analysis of the composition of the fractions containing the biologically active metabolites and of the volatile fractions, by gas chromatography-mass spectrometry (GC-MS), of both essential oil and headspace sampled by headspace solid-phase microextraction (HS-SPME) are here shown to be effective in discriminating the poisonous and nonpoisonous chemotypes. HS-SPME with CAR/PDMS/DVB in combination with GC-MS has also been found to be a successful, fully automated one-step method for rapid and unequivocal discrimination of the two chemotypes, using aristolene and allohedycaryol as markers of the poisonous and nonpoisonous chemotypes, respectively.

The essential oils of Ridolfia segetum (L.) Moris and Oenanthe crocata L. (Apiaceae), collected in Sardinia (Italy), have been assayed for two enzyme-associated activities of the HIV-1 reverse transcriptase (RT): RNA-dependent DNA polymerase (RDDP) activity and ribonuclease H (RNase H) activity. In biochemical assays, the essential oils inhibited HIV-1 RT RDDP activity in a dose-dependent manner, while they were inactive towards RNase H activity. Furthermore, the oils were cytotoxic towards K (562) cell replication. GC-MS analysis of the essential oils obtained by steam distillation of the aerial parts showed that the main components of R. segetum were alpha-phellandrene, alpha-terpinolene, beta-phellandrene, and dillapiol and those of O. crocata were sabinene, TRANS-beta-ocimene, CIS-beta-ocimene, and beta-pinene.