Four kinds of fresh sweet oranges were obtained in the same season, November 2000, in Guangzhou. Citrus sinensis var. Hongjiang (called 'hong jiang chen' in Chinese) and C. sinensis Osbeck var. Anliu (called 'luo gang chen') were obtained at an orchard in Luo gang in Guangzhou (25 km from the center of Guangzhou). Citrus sinensis var. Sihui (called 'sihui ju') was harvested at the Shigou Experimental Farm in Sihui City in Guangdong Province (75 km far away from Guangzhou). Citrus sinensis var. Washington navel (called 'qi chen') which was produced in Jiangxi Province (200 km from Guangzhou; bordering Guangdong Province), was purchased at the wholesale market in Guangzhou. All oranges were kept in a cold room until prepared a few days later.

The peel oil compositions of four kinds of sweet oranges in China, Citrus sinensis Osbeck var. Hongjian, C. sinensis Osbeck var. Anliu, C. sinensis Osbeck var. Sihui and C. sinensis Osbeck var. Washington navel, were investigated by GC and GC/MS. The essential oils were extracted by cold-pressing method. Forty-two to 53 compounds were quantitatively determined for each variety. Their percentages, respectively, were: > 97.3%, > 98.4%, > 97.5% and > 98.0% in hydrocarbons; > 1.5%, > 0.7%, > 0.8% and > 0.9% in total aldehydes; 0.8%, 0.5%, 0.5% and 0.5% in alcohols. Either cis-or trans-limonene oxide was detected in small amounts in each of the four samples, with Hongjiang containing both limonene oxides. delta-3-Carene was commonly quantified at a level of 0.1% in all the samples. The content of aliphatic aldehydes, including octanal, nonanal, decanal and dodecanal, exceeded that of terpene aldehydes, such as neral and geranial in Hongjiang (0.9%) and Washington navel (0.6%), whereas the aliphatic aldehydes in Anliu and Sihui were present to a lesser degree than the terpene aldehydes. Either alpha- or beta-sinensal was detected in trace amounts in each of the four samples. Linalool was the major alcohol in all the samples. Nootkatone was not detected.

The aerial parts of flowering Mentha pulegium plants (cut at ground level) and individual M. pulegium plants were collected in the summer (July, 2003) from three wild populations located in the Municipality of Laganas, Zakynthos, W. Greece. Location 1 (N 37° 41′ 29″, E 20° 50′ 25″; map datum WGS 84; altitude 3 m; 14/07/03) was close to Keri Beach (Limni Keriou), Location 2 (N 37° 43′ 34″, E 20° 50′ 41″; altitude 3 m; 13/07/03) was near the village of Kalamaki and Location 3 (N 37° 39′ 39″, E 20° 48′ 44″; altitude 160 m; 17/07/03) was near the village of Vasilikos. The three locations are within the mainland limits of the protected area of the National Marine Park of Zakynthos (NATURA 2000 Network, site GR 2210002; 14).

The composition of the inflorescence (I), leaf (L) and stem (S) essential oils of wild Mentha pulegium plants from three populations (1-3) on the island of Zakynthos were examined. Pulegone (32.8 %, S1 to 75.8 %, I3) was the major constituent of all of the oils. The other main constituents were piperitenone (5.1 %, L3 to 35 %, I2), isomenthone (4.3 %, I2 to 28.6 %, L3) and piperitone (0.5 %, I3 to 5.2 %, L2). In total, C-3-oxygenated p-menthane compounds constituted from 73.0 % (S1) to 96.2 % (I2) of the oils. The piperitenone content of the inforescence oils was up to 2.4 (Loc 3) times higher than that of the leaf oils. Correspondingly, the isomenthone content of the leaf oils was up to 4.2 (Loc 2) times higher than that of the inforescence oils. The ratio of the isomenthone:piperitenone content of the oils (n=3) was markedly different for the inforescence (mean 0.31), leaf (mean 2.91) and stem (mean 1.12) oils.

The aerial parts of flowering Mentha spicata plants (cut at ground level) and individual M. spicata plants were collected in the summer (July, 2003) from three wild populations located in the Municipality of Laganas, Zakynthos, W. Greece. Location 1 (N 37° 39′ 39″, E 20° 48′ 44″; map datum WGS 84; altitude 160 m; 14/07/03) was near the village of Keri, Location 2 (N 37° 41′ 29″, E 20° 50′ 25″; altitude 3 m; 14/07/03) was close to Keri Beach (Limni Keriou) and Location 3 (N 37° 43′ 34″, E 20° 50′ 41″; altitude 35 m; 14/07/03) was near the village of Pandocratoras. The three locations are within the mainland limits of the protected area of the National Marine Park of Zakynthos (NATURA 2000 Network, site GR 2210002; 8).

The main oil constituents were trans-piperitone oxide, piperitenone oxide and 1,8-cineole. On a whole plant basis (aerial parts) the trans-piperitone oxide content ranged from 1.4 % location (Loc 1) to 32.5% (Loc 3) and appeared to have an inverse relationship with the 1,8-cineole content which ranged from 10.8 % (Loc 3) to 37.9 % (Loc 1). 1,8-cineole was the major oil constituent (37.9 %) of M. spicata plants from Loc 1. The major constituent of the inflorescence oils was piperitenone oxide which ranged from 32.4 % (Loc 3) to 46.3 % of the oil (Loc 1). The major constituent of the leaf oils was 1,8-cineole (40.5 %) in plants from Loc 1 and trans-piperitone oxide in plants from Loc 2 (19.8 %) and Loc 3 (33.5 %). This is the first report for wild populations in Greece of a M. spicata oil in which 1,8-cineole is the major constituent. The observed variation in essential oil composition between locations and plant organs in July would not appear to be directly related to the climatic conditions.