KEYWORDS
Rocky desertification, Akebia trifoliata , Secondary metabolites,
Medicinal ingredients
1 | INTRODUCTION
Karst rocky desertification is a process of land degradation caused by
human activities, which is widely distributed in Southwest China,
especially in Guizhou, and has become one of the three major ecological
disasters in China (Wang et al., 2010; Stas et al., 2017). With the
aggravation of rocky desertification, a large amount of soil loss leads
to insufficient water accumulation, which leads to the decrease of soil
water holding capacity and the stability of surface soil aggregates.
Therefore, the nutrient content of rocky desertification soil is
significantly different from that of normal soil (Sheng et al., 2018;
Wang et al., 2018; Ma et al., 2020). In recent years, many scholars have
tried to use plants to ecological restoration of rocky desertification,
and the effect has only been restored, and its economic value is very
small. Therefore, it is very important to find the economic value of
vegetation repaired in rocky desertification habitat.
Plant secondary metabolism is the result of interaction between plant
and environment in the long-term evolutionary process. Secondary
metabolites and related enzymes play an important role in protecting and
coordinating plants to adapt to external stress environment (Theis and
Lerdau 2003; Ajmal et al., 2011). Secondary metabolites are not only
involved in many kinds of plant resistance processes, but also have
antioxidant, anti-inflammatory and anticancer effects. They can reduce
the incidence of cancer, breast cancer and colon cancer (Romagnolo and
Selmin 2012; Bhatia et al., 2011; Nourimand and Mohsenzadeh 2012), For
example, polyphenols are a kind of secondary metabolites produced by
plant phenylpropane and flavonoid metabolic pathways. They not only
participate in plant growth and development, but also give plants the
ability to resist ultraviolet, antioxidant and free radicals (Dixon et
al., 2005; Skerget et al., 2005). They also have functions of preventing
hypertension, hyperlipidemia (Prasain et al., 2010), diabetes (Rodrigo
et al., 2011) and anticancer (Araùjo et al., 2011). Flavonoids are
natural antioxidants that can directly scavenge oxygen free radicals and
reactive oxygen species (Terao 2009), but also prevent osteoporosis and
reduce the risk of colon cancer, prostate cancer and breast cancer
(Michihara et al., 2012; Priya and Sharma 2013). Tannin is a good free
radical scavenger and lipid peroxidation inhibitor (Dicko et al., 2005),
with good physiological functions such as astringency, anti diarrhea,
antibacterial, antioxidant and antiviral (Frasca et al., 2012).
Therefore, the potential economic value of secondary metabolites in
plants is very great. The synthesis of these substances is regulated by
the phenylpropane pathway in plants, and the main enzymes regulated by
it include PAL (Phenylalanine ammonialyase), C4H
(Cinnamate-4-Hydroxylase) and 4CL (4-Coumarate: Coenzyme A Ligase)
(Hahlbrock and Scheel 2003; Singh et al., 2009).
Akebia trifoliata is one of the economic species selected to
control rocky desertification habitat in recent years, and has achieved
good results. Its fruit is not only edible, but also can be used to make
oil (Jiang et al., 2020). At the same time, it has the functions of
promoting blood circulation, anti-inflammatory and diuretic (Jiang et
al., 2012). Its extract can significantly inhibit the survival and
proliferation of liver cancer cells (Lu et al., 2019). The main
medicinal components of A. trifoliata are oleanolic acid,
α-hederagenins and some secondary metabolites, such as polyphenols,
tannins and flavonoids, which affect the synthesis of A.
trifoliata . For example, drought can increase the content of
artemisinin in Artemisia carvifolia (Yadav et al., 2014),
saikosaponin a and saikosaponin b in Bupleurum chinense will
increase under moderate water stress (Zhu et al., 2009), and Himalayan
vegetation will secrete a lot of polyphenols and alkaloids due to
long-term exposure to natural factors such as ultraviolet, drought and
strong wind (Bhatia et al., 2011). However, these changes are different
in different plants and different stress intensities (Zahir et al.,
2014). But so far, there have been no reports on the effects of rocky
desertification habitat on the content of secondary metabolites and
related enzymes of A. trifoliata .
In this study, we compared the changes in the secondary metabolites and
related enzymes of A. trifoliata in rocky desertification
habitats and normal habitats, and attempted to clarify the response
mechanism of the secondary metabolites and related enzymes of A.
trifoliata in rocky desertification habitats. Meantime, it also
provides a theoretical basis for the development of A. trifoliatamedicinal resources.
2 | MATERIALS AND METHODS
2.1 | Experimental site
Ludi village, Shiban Town, Huaxi District, Guiyang City, Guizhou
Province China (Huaxi base) and Zhongzhai village, Huajiang Town,
Guanling County, Anshun City (Guanling base) were used as experimental
sites (one of them was used as a repetition). The annual rainfall is
mainly concentrated in April to October. One rocky desertification
habitat (> 1000 m2) is selected in each
area, and one normal habitat (non rocky desertification area) is
selected as the control (> 1000 m2). The
geographic and meteorological data of each base were from the archives
of Guizhou Meteorological Bureau (Table 1). It can be seen from table 1
that Huaxi base and Guanling base had similar environmental factors,
which were the two repeated treatments of the experiment. This study
focuses on the effects of rocky desertification habitat on secondary
metabolites of A. trifoliata , and the different performance of
plants came from the effects of rocky desertification habitat rather
than the different conditions of different bases.
TABLE 1 The geographical and meteorological data of different
bases