Study on the chemistry of small grain coffee in Yunnan, Kunming Institute of plants, Chinese Academy of Sciences

Professional coffee knowledge exchange more coffee bean information please follow the coffee workshop (Wechat official account cafe_style)

Coffee is one of the most popular beverages in the world, and its composition and physiological function have always been the focus of scientists all over the world. As the largest emerging coffee consumption market in the world, China has not only attracted the attention of a large number of investors, but also promoted the rapid development of the planting and processing industry of agricultural small grain coffee with Yunnan plateau characteristics. According to incomplete statistics, in 2017 and 2018, the planting area of Yunnan small-grain coffee reached 1.8 million mu, and the total annual output of Yunnan small-grain coffee reached 164700 tons, accounting for 1.7% of the world's coffee production in the same period and more than 99% of China's coffee production. What is out of proportion to the huge production and consumption of coffee in China is the lack of continuous mining of natural active functional molecules in Yunnan coffee, especially the study on the chemical composition and function of Yunnan small grains, which is still blank except for routine analysis. Qiu Minghua Research team of Kunming Institute of Botany, Chinese Academy of Sciences conducted an in-depth study on the chemical constituents of Yunnan small-grain coffee fruits and seeds, and established a technical system for rapid analysis of coffee chemical constituents by NMR. More than 40 new natural chemical structures were discovered from various coffee samples from Yunnan, opening up some new coffee molecular resources for the study of coffee chemical components around the world. A study on the inherent relationship between coffee flavor characteristics and chemical components is under way.

1. New diterpenoid glycosides from cooked beans of Yunnan small Coffee

Coffee cooked beans refer to roasted coffee seeds, which are ground, brewed and filtered to get coffee drinks. The chemical study on the extract of Yunnan small grain coffee ripe bean from Pu'er showed that most of the diterpenoids in the ripe bean existed in the form of glycosides, from which four new enantiomeric kaurane type (ent-kaurane) diterpenoid glycosides were found. At the same time, a small number of enantiomeric-coastal twin flower alkane (villanovane) diterpenoid glycosides were found in nature for the first time, which enriched people's understanding of diterpenoids in coffee beans. However, these chemical constituents had no inhibitory activity on HL-60, SMMC-7721, AME 549, MCF-7 and SW4805 tumor cell lines. The results were published in Journal of Agricultural and Food Chemistry under the title Characterization of diterpenoid glucosides in roasted Puer coffee beans (2014, 62RU 2631-2637).

2. Discovery of new coffee diterpene lactone in Yunnan small-grain coffee

Caffeine alcohol is a diterpene in coffee. Generally, the A ring of diterpenes contains a tetrahydrofuran ring. However, eight caffeol diterpenes in the A ring of Yunnan small grain coffee contained an unsaturated g-lactone and cyclic group, and a new class of caffeine diterpene lactones (cafestolactone) was isolated from coffee for the first time. There are a large number of fatty acid compounds 1-8 of new coffee diterpene lactones in Yunnan small-grain coffee raw beans (figure 2).

The fatty acids in compound 1-8 were identified by GC analysis except for NMR identification. Among these coffee diterpene lactone compounds, compounds 3pyrine 4 and 6 showed certain platelet aggregation activity in vitro, and the induction rates were 11.4%, 15.8% and 7.8%, respectively, at the concentration of 0.4mg/ml. The structure and activity of these compounds are published in Food Chemistry under the title Identification of new diterpene esters from green Arabica coffee beans, and their platelet aggregation accelerating activities. 2018, 263, 251 257 .

3. Discovery of new diterpenes and coffee diterpene lactones from the fruits of Yunnan small-grain coffee.

37 chemical constituents were isolated and identified from the coffee fruits (sun beans) of Yunnan small grain coffee variety DR132 (Huangguo), of which 5 were new diterpenoids (figure 3). The new compound caffruenol Amuri B (1-2) is a new diterpene with 18 and 19 methyl rearrangement to Δ (4jue 18), which has never been reported. In addition to new coffee diterpene alcohols, six new caffeine diterpene lactones (cafestolactone) were isolated from coffee, including three new compounds (3-5), which confirmed the existence of diterpenoid diterpenes in Yunnan small grain coffee. At present, caffeol diterpene lactone (cafestolactone) compounds have not been reported in the chemical constituents of coffee from other countries and regions, and whether they are the comparative characteristics of Yunnan small-grain coffee needs comparative study. The above research results were recently published in Fitoterapia under the title of Ent-kaurane diterpenoids from the cherries of Coffea arabica. 2019, 132VR 7-11 (doi:10.1016/ j.fitote.2018.08.023).

4. Neodamane triterpenes from the fruits of Yunnan small-grain coffee.

Four new dammarane triterpenes (caffruones Amurd) were also found from the dried fruits of DR 132, a yellow-skinned coffee variety bred by Yunnan Dehong Thermal Research Institute. This is the first time that tetracyclic triterpenes have been found in the genus Coffee (Fig. 5), indicating the structural diversity of secondary metabolic components and rich molecular resources in Yunnan small-grain coffee. The results are published in Natural Products and Bioprospecting, 2018.

The research project on the chemical composition and activity of Yunnan small grain coffee is supported by the National Natural Science Foundation of China (No.31670364), the key New products Program of Yunnan Province (2015BB002), the special fund of Pu'er City (2017), Qiu Minghua expert workstation project (2018) and the National key Room Open Foundation project of phytochemistry (P2015-ZZ09). These research results have made a large number of new discoveries on the chemical constituents and functions of small-grain coffee in China, and laid the foundation for the rapid development of coffee industry in China.