Chemical investigation of the volatile compounds of Alpinia zerumbet leaves using DH-TD-GC/MS

The aromatic perennial plant Alpinia zerumbet (Pers.) Burtt & Smith (Zingiberaceae) grows in Japan, from the southern Kyushu to the Ryukyu Islands. Recently, interspecific hybridization of Alpinia spp. was reported in Taiwan. We have demonstrated that the floral volatiles of A. zerumbet differ between individual plants [1]. We also showed that the yield, content of the major volatile compounds, enantiomeric ratio of some monoterpenes, and antioxidant activities of the A. zerumbet leaf essential oils varied significantly among individual plants [2], which reflected genetic variability within the species. However, this trend needed to be demonstrated with more individuals. Unfortunately, a large quantity of leaves is necessary to obtain sufficient essential oil to investigate the differences in the chemical composition of the oils among individuals, because A. zerumbet leaves yield only a small amount of the essential oil upon hydrodistillation (0.01–0.07%). Prompted by this, here, we combined the dynamic headspace method with thermal desorption-gas chromatography-mass spectrometry (DH-TD-GC/MS). For this method, a small piece of a leaf is used and sampling is possible directly in the field. The aims of this study were to test the effectiveness of this DH-TD-GC/MS method and reveal the variation in the chemical composition of the essential oils of the leaves among the individual plants.                A. zerumbet leaves were collected from Okinawa and Ie (16 and 22 samples, respectively), the Ryukyu Islands, between May and October 2017. The leaves were oven-dried (40–45 °C) to a moisture content of 10% or less, and 0.5 g of the dried leaves and stems from individual plants were septum-sealed in a 27-mL gas-tight vial. After introducing air through the activated carbon trap into the vial, volatiles were aspirated by a minipump and adsorbed to Tenax TA (60/80 mesh, 130 mg) for 10 min at 60 °C. Chemical analysis was performed using a TD-GC/MS system. The major volatiles identified in this study (α-pinene, camphene, limonene, β-phellandrene, 1,8-cineole, p-cymene, camphor, linalool, and cryptone) well represented the characteristics of the essential oil of the leaf. The aroma profile obtained here also confirmed that the volatiles in the leaves clearly differed among individual plants. These observations suggest the plausibility of selecting lineages of A. zerumbet to optimize the future production of valuable essential oils

Improving the efficiency of essential-oil extraction from Abies sachalinensis with an underwater shockwave pretreatment

Abies sachalinensis (Sakhalin fir) is a conifer species belonging to the family Pinaceae that is native to and widely distributed throughout Sakhalin Island, the southern Kurils (Russia), and northern Hokkaido (Japan). The essential oil of A. sachalinensis has been found to be an active removal agent, similar to γ-terpinene, myrcene, and β-phellandrene, which effectively remove nitrogen dioxide. Essential oils provide a relaxing effect; the use of essential oils is expected to improve overall air quality.                Underwater shockwaves generate instantaneous high pressure that reaches the entire cell and causes multiple cracks along the tracheids, causing the pit membrane to flake off through spalling destruction. These cracks function as permeation pathways [1]; this application was expected to result in a more effective essential oil extraction by subsequent steam distillation [2]. We, herein, introduce a novel application of this pretreatment process aimed at improving the efficiency of essential-oil extraction from A. sachalinensis leaves and branches. A. sachalinensis leaves and branches were oven-dried (40-45 °C) to a moisture content of 10% or less, and were subjected to the shockwave pretreatment or left untreated before essential-oil extraction by steam distillation. Chemical analysis was performed using gas chromatography-mass spectrometry. The essential-oil yields of raw untreated and untreated dried leaves were 5.1 and 2.4 g/kg of leaf dry weight (DW), respectively. Upon application of a 3.0 kV, 3.6 kJ shockwave, the essential-oil yield increased with the number of shockwave cycles; the yield was 32.7 g/kg DW after 10 cycles, a 13.6-fold increase compared to that of the untreated dried leaves. In addition, sesquiterpenes increased by more than 30-fold in content compared to that of untreated dried leaves. Thus, these results suggest that instantaneous high-pressure treatment, as a pretreatment for conventional steam distillation, has a distinct advantage in increasing the essential-oil yield and extracting the bioactive components. Furthermore, this method also can be used for the pretreatment of microwave essential-oil extraction or steam distillation under reduced pressure

Underwater Shockwave Pretreatment Process to Improve the Scent of Extracted Citrus junos Tanaka (Yuzu) Juice

Citrus junos Tanaka (yuzu) has a strong characteristic aroma and thus its juice is used in various Japanese foods. Herein, we evaluate the volatile compounds in yuzu juice to investigate whether underwater shockwave pretreatment affects its scent. A shockwave pretreatment at increased discharge and energy of 3.5 kV and 4.9 kJ, respectively, increased the content of aroma-active compounds. Moreover, the underwater shockwave pretreatment afforded an approximate tenfold increase in the scent intensity of yuzu juice cultivated in Rikuzentakata. The proposed treatment method exhibited reliable and good performance for the extraction of volatile and aroma-active compounds from the yuzu fruit. The broad applicability and high reliability of this technique for improving the scent of yuzu fruit juice were demonstrated, confirming its potential for application to a wide range of food extraction processes

Improving the Efficiency and Antioxidant Activity of Essential Oil Extraction from Abies sachalinensis by Underwater Shockwave Pretreatment for the Construction of Low-Energy and Sustainable Essential Oil Extraction System

Essential oils (EOs) from Abies sachalinensis (Sakhalin fir), a conifer species found in Sakhalin Island and Hokkaido in Japan, effectively remove nitrogen dioxide and possess antifungal activity. EOs also exert a relaxing effect and enhance air quality. Underwater shock waves generate instantaneous high pressure that ruptures cell walls, enhancing the performance of steam distillation and oil extraction. In this study, we aimed to increase the yield and quality of A. sachalinensis extracts using shockwaves. Leaves and branches were subjected to shockwave pretreatment or left untreated before EO extraction by steam distillation. EO yield of untreated dried leaves was 2.4 g/kg of dry leaf weight (DW). Upon application of a 3.0 kV, 3.6 kJ shockwave, the yield increased with the number of shockwave cycles. After ten cycles, yield increased 13.6-fold. Pretreatment with shockwaves for 10 cycles resulted in approximately 6- and 13-fold reductions in total energy consumption relative to fresh and dried leaves, respectively. Antioxidant activity increased more than 30-fold in shockwave-pretreated leaves than in untreated dried leaves after 10 cycles. This novel process can significantly reduce the energy used for EO extraction in steam distillation, thereby contributing to the development of a sustainable, low-energy EO production system