1 Introduction

Corydalis yanhusuo, commonly known as Yuanhu or Yanhusuo, belongs to the Papaveraceae family and is a valuable medicinal plant. It is native to East Asia, particularly China, and has been widely used in traditional medicine as a key component in various herbal formulations (Zhang et al., 2020a). Corydalis yanhusuo was first documented in the Kaibao Bencao and is known for its properties of promoting blood circulation, regulating qi, and relieving pain (Liu and Liu, 2012, Capital Medicine, (3): 47). The primary medicinal part of Corydalis yanhusuo is its dried tuber, renowned for its efficacy in treating various pain-related symptoms (Yuan et al., 2004; Tian et al., 2020; Li et al., 2022). With the increasing demand for Corydalis yanhusuo in the pharmaceutical industry, developing efficient cultivation techniques that enhance both yield and alkaloid content has become particularly crucial. Such advancements would significantly improve its medicinal and economic value (Sagare et al., 2000; Li et al., 2022).

The cultivation of Corydalis yanhusuo faces numerous challenges. This plant has stringent requirements for soil conditions, climatic environment, and nutrient management, which directly determine its optimal growth state and efficient alkaloid production. However, traditional cultivation methods often result in significant yield fluctuations and unstable alkaloid content, making it difficult to meet the strict standards of medicinal quality (Sagare et al., 2000). Studies have shown that when Corydalis yanhusuo is rotated with crops such as peanuts, the tuber yield may significantly decrease, though under specific field conditions, its yield can improve (Li et al., 2022). Additionally, the plant's high sensitivity to pests and diseases greatly affects its yield, raising the need for more stringent and effective pest and disease control measures. Enhancing alkaloid content represents another major challenge in the cultivation of Corydalis yanhusuo, as it is influenced by a combination of factors including soil fertility, environmental conditions, and genetic traits (Du et al., 2018; Chen et al., 2020). A deeper understanding of the synergistic effects of these key variables, coupled with optimized cultivation management strategies, is essential for achieving efficient production and enhancing the medicinal value of Corydalis yanhusuo.

This study systematically analyzes the cultivation techniques and primary active compounds of Corydalis yanhusuo, aiming to develop efficient cultivation methods that enhance its yield and increase the alkaloid content in its tubers. The study explores methods for soil improvement, optimization of environmental conditions, and the implementation of advanced pest and disease management strategies, aiming to address the challenges present in traditional cultivation practices and provide practical solutions for farmers and producers. The findings of this study may also offer broader insights for the cultivation of other medicinal plants, contributing to the development of more efficient and sustainable agricultural practices in the herbal medicine sector.

2 Characteristics and Traditional Cultivation Techniques of Corydalis yanhusuo

2.1 Morphology and growth habits

Corydalis yanhusuo is a herbaceous perennial plant native to East Asia, particularly China and Japan. The plant grows to a height of 15-30 cm, featuring delicate, fern-like compound leaves with a bluish-green hue. Its flowers, which typically bloom from April to May, are purple to lavender in color, borne in clusters at the terminal ends of stems (Figure 1) (Wan et al., 2019; Wu et al., 2021). The tubers of Corydalis yanhusuo, which are irregularly globose or ovate in shape, are the main storage organs and are harvested for medicinal use (Zhao et al., 2023).

Corydalis yanhusuo thrives in temperate climates at altitudes of 500-1,500 meters, preferring loose, well-drained, fertile soils rich in organic matter. It favors a semi-shaded and humid environment and exhibits a unique growth cycle. Starting with vegetative growth in early spring, the plant progresses through flowering and tuber development, and by late summer, its aboveground parts wither as it enters dormancy, while the tubers continue to mature underground (Liao et al., 2016). The morphology and growth habits of Corydalis yanhusuo are closely linked to its ecological requirements, making its cultivation heavily reliant on replicating optimal environmental conditions.

2.2 Active compounds and their health benefits

Corydalis yanhusuo is renowned for its abundance of bioactive alkaloids, the most notable being tetrahydropalmatine (THP), corydaline, dehydrocorybulbine (DHCB), and corydalmine. These alkaloids are primarily responsible for the plant’s medicinal properties, which have been extensively used in traditional Chinese medicine (Wu et al., 2014; Du et al., 2018; Wang et al., 2020). Among these, THP is recognized for its analgesic and sedative effects, acting as a natural pain reliever by inhibiting specific dopamine receptors in the central nervous system. This has made C. yanhusuo a popular choice for treating ailments such as menstrual cramps, headaches, and joint pain (Wu et al., 2014; Wu et al., 2018). Dehydrocorybulbine (DHCB), another significant compound, has gained attention for its pain-relieving effects and ability to reduce neuropathic pain. 

The alkaloids in C. yanhusuo also exhibit anti-inflammatory and muscle-relaxant properties, broadening their therapeutic applications (Zhang et al., 2020a). Pharmacological studies have further highlighted the potential of these alkaloids in regulating mood and alleviating anxiety, suggesting that C. yanhusuo may be effective in treating mental health conditions such as depression and anxiety. In mouse experiments, nuclear magnetic resonance (NMR) metabolomics analysis demonstrated that total alkaloids from C. yanhusuo significantly improved metabolic disturbances in a chronic unpredictable mild stress (CUMS) model (Wu et al., 2015).

2.3 Traditional cultivation techniques

The traditional cultivation of Corydalis yanhusuo has a history spanning several centuries, primarily in regions with a long-standing tradition of traditional Chinese medicine, such as Sichuan and Zhejiang provinces in China (Li et al., 2017). The cultivation process begins with the selection of high-quality tubers, which are commonly used as planting materials. Planting typically takes place in the autumn, as C. yanhusuo requires a cold period to break dormancy and stimulate subsequent growth. Traditional farmers usually choose loamy soil with good water retention to support optimal tuber development and ensure fields are located in shaded areas to mimic the plant's natural growth conditions under forest canopies. Before planting, the soil is often enriched with organic compost to enhance fertility, as C. yanhusuo demands abundant nutrients during its vegetative growth phase. Tubers are generally planted at a depth of 5-10 cm with adequate spacing to allow for tuber expansion (Zhao et al., 2023). Irrigation is crucial during the early growth stages, with soil moisture maintained at stable levels to support root development. However, waterlogging must be avoided to prevent tuber rot, which could severely impact yield and quality.

Traditional cultivation practices also involve manual weeding and close monitoring of pest and disease management, typically employing natural pest control methods and crop rotation. A common practice is rotating with crops such as peanuts to enhance land use efficiency, though this can sometimes result in reduced tuber yields (Li et al., 2022). Harvesting usually occurs in late spring or early summer when the aboveground parts begin to wither, signaling that the tubers have matured. The harvested tubers are then cleaned, dried, and processed for use in medicinal formulations.

3 Research and Application of Efficient Cultivation Techniques of Corydalis yanhusuo

3.1 Soil improvement and nutrient management

Improving soil quality and managing nutrients effectively are crucial for the efficient cultivation of Corydalis yanhusuo. Studies have shown that soil physicochemical properties such as cation exchange capacity (CEC), soil organic matter (SOM), total nitrogen (TN), and pH value significantly influence the growth and yield of C. yanhusuo. For instance, fields previously subjected to flooding exhibited higher yields compared to those rotated with peanuts or left without rotation, primarily due to improved soil properties and beneficial changes in the rhizobacteriome (Li et al., 2022). 

Additionally, intercropping with local crops like rice, maize, and peanut has been found to enhance soil quality by increasing soil pH, nitrogen-cycling-gene abundances, and beneficial microorganism populations, which in turn improve the biomass and secondary metabolite content of the plants (Liu et al., 2023).

3.2 Control of environment

Controlling environmental factors such as light, temperature, and humidity is essential for optimizing the growth conditions of Corydalis yanhusuo. For instance, maintaining an appropriate range of light and temperature can significantly influence the biosynthesis of its key active compounds, benzylisoquinoline alkaloids (BIAs) (Xu et al., 2021). Corydalis yanhusuo thrives best under partial shading; excessive sunlight may cause leaf scorching, while insufficient light can hinder tuber formation. Using adjustable shading nets to provide a balanced light environment can optimize photosynthesis and promote healthy growth (Bao et al., 2020).

The optimal temperature range for Corydalis yanhusuo growth is 15 °C to 25 °C, as extreme temperatures may impede root development or trigger premature bolting (Li et al., 2022). Additionally, maintaining 60%–70% humidity during the early growth stages supports healthy leaf and tuber development. However, measures should be taken to avoid excessive moisture, which could lead to fungal infections.

3.3 Planting density and intercropping techniques

Planting density and intercropping techniques play a crucial role in the efficient cultivation of Corydalis yanhusuo. An appropriate planting density is a key factor in maximizing yield and alkaloid content. Proper spacing ensures that each plant receives sufficient light, water, and nutrients. Studies have shown that planting 25-30 plants per square meter can achieve high yields while avoiding resource competition (Liu et al., 2023). These intercropping systems help mitigate the challenges of continuous cropping and enhance the overall sustainability of Corydalis yanhusuo cultivation.

Intercropping can further improve productivity, especially when Corydalis yanhusuo is paired with complementary crops that do not compete for the same nutrients. For instance, intercropping with legumes can improve soil fertility through natural nitrogen fixation, reducing the need for chemical fertilizers (Feng et al., 2021). Additionally, intercropping with aromatic plants like garlic or marigold can provide natural pest control, fostering a healthier growing environment (Pokharel et al., 2023).

3.4 Pest and disease management

Corydalis yanhusuo is susceptible to various common pests and diseases that can significantly impact its yield and quality. Major pests include aphids, caterpillars, and root-knot nematodes, which feed on the plant's leaves and roots, causing stunted growth and reduced alkaloid production (Ali et al., 2018; Holbein et al., 2019). Common diseases such as powdery mildew and root rot are particularly problematic in areas with high humidity. Powdery mildew primarily affects the aboveground parts of the plant, while root rot is often associated with poorly drained soils and, if left unmanaged, can lead to severe losses (Huang et al., 2021; Rosati et al., 2023). Environmental conditions such as excessive moisture and poor ventilation exacerbate these issues, making timely identification of pests and diseases essential for effective management. Regular monitoring of C. yanhusuo cultivation areas can help detect early signs of infestation and implement preventive measures to minimize the spread and impact of these problems, ensuring crop health and productivity.

To reduce chemical residues and promote environmental sustainability, organic pest and disease control methods are increasingly adopted in Corydalis yanhusuo cultivation. Biological control agents, such as ladybugs and lacewings, are effective in controlling aphid populations. Additionally, plant-based insecticides like neem oil are commonly used to repel pests without harming beneficial insects (Tamilselvi et al., 2022). Crop rotation is another effective organic strategy, breaking the life cycles of pests and pathogens and reducing the incidence of root-knot nematodes and soil-borne diseases (Li et al., 2022). The use of organic compost and mulching not only improves soil fertility but also supports the growth of beneficial microorganisms that suppress harmful pathogens. By integrating these organic approaches, farmers can effectively manage pest and disease pressures while maintaining ecological balance.

4 Factors Influencing Alkaloid Content

4.1 Environmental factors

Environmental factors play a crucial role in determining the alkaloid content in Corydalis yanhusuo. One significant environmental factor is the type of field conditions under which the plant is cultivated. For instance, fields that have been previously flooded (HR fields) have shown an increased yield of C. yanhusuo compared to fields used for peanut rotation (PL fields) or fields without any rotation or flooding (N fields) (Li et al., 2022). This suggests that water availability and soil moisture levels can significantly impact the plant's growth and alkaloid production. Additionally, climatic variations have been found to correlate with alkaloid content in cultivated populations of C. yanhusuo, indicating that temperature, humidity, and other climatic factors can influence the biosynthesis of alkaloids (Chen et al., 2020).

4.2 Genetic variability and selection

Genetic variability and selection are also pivotal in influencing the alkaloid content of C. yanhusuo. Research indicates that there is a significant relationship between genetic and epigenetic variation in both natural and cultivated populations of C. yanhusuo (Chen et al., 2020; Zang et al., 2023). Genetic variation was found to be slightly higher in natural populations compared to cultivated ones, while epigenetic differentiation was more pronounced among cultivated populations. This suggests that selective breeding and cultivation practices can lead to genetic and epigenetic modifications that impact alkaloid biosynthesis. Moreover, the alkaloid content in cultivated populations was significantly correlated with genetic (6.89%) and epigenetic (14.09%) variations, highlighting the importance of genetic selection and breeding strategies in enhancing alkaloid production (Chen et al., 2020).

4.3 Processing methods

Processing methods also have a significant impact on the alkaloid content in Corydalis yanhusuo. Different processing methods, such as steaming, frying, or alcohol-steaming, can alter the structure and internal chemical environment of Corydalis yanhusuo, thereby affecting the extraction and stability of alkaloids. The study shows that vinegar processing or ethanol extraction has a significant impact on the extraction efficiency and stability of major alkaloids in Corydalis yanhusuo (such as tetrahydropalmatine, corydaline, etc.). For instance, vinegar processing has been proven to enhance the absorption rate of alkaloids in multiple tissues, while reducing toxicity, thereby improving both efficacy and safety (Wu et al., 2021; Wang et al., 2022). 

Therefore, selecting appropriate processing methods is crucial for maintaining and enhancing the alkaloid content in Corydalis yanhusuo. In practical applications, traditional experience should be combined with modern scientific research to optimize processing techniques, ensuring the quality and efficacy of the medicinal material.

5 Strategies for Enhancing Alkaloid Content in Corydalis yanhusuo

5.1 Genetic breeding and selection of elite varieties

Genetic breeding and the selection of elite varieties are fundamental strategies for enhancing the alkaloid content in Corydalis yanhusuo. Studies have shown that genetic and epigenetic variations play a significant role in the alkaloid content of C. yanhusuo. For instance, cultivated populations of C. yanhusuo exhibit higher epigenetic differentiation compared to natural populations, which is correlated with variations in alkaloid content (Chen et al., 2020). This suggests that selective breeding focusing on both genetic and epigenetic traits could be a viable approach to enhance alkaloid production. Additionally, the identification of specific genes involved in the biosynthesis of benzylisoquinoline alkaloids (BIAs) through full-length transcriptomic and metabolomic analyses provides a genetic basis for breeding programs aimed at increasing the concentration of these bioactive compounds (Xu et al., 2021).

5.2 Biotechnology approaches

Biotechnology offers advanced tools for enhancing alkaloid content in C. yanhusuo. Techniques such as full-length transcriptomics and targeted metabolomics have been employed to identify key genes involved in the BIA biosynthetic pathway, which can be targeted for genetic modification to boost alkaloid production (Xu et al., 2021; Zhao et al., 2024). For example, O-methyltransferases (OMTs) play a key role in the synthesis of BIAs, and an in-depth analysis of their function can help understand the biosynthetic mechanisms of alkaloids in Corydalis yanhusuo, providing theoretical support for subsequent metabolic engineering and drug development (Figure 2) (Zhao et al., 2024). Moreover, the use of high-throughput screening assays to identify and validate the activity of specific alkaloids, such as those acting as dopamine receptor antagonists, can help in the selection of high-yielding varieties (Wu et al., 2018). These biotechnological approaches not only facilitate the identification of valuable genetic traits but also enable the precise manipulation of metabolic pathways to enhance the production of desired alkaloids.

5.3 Exogenous substance induction and regulation techniques

The application of exogenous substances to induce and regulate alkaloid biosynthesis is another effective strategy. For example, the use of specific solvents and pH conditions during the extraction and purification process has been optimized to maximize the yield of various alkaloids in C. yanhusuo (Zhang et al., 2020b). Additionally, environmental factors such as soil physicochemical properties and rhizobacteriome composition, influenced by practices like peanut rotation and flooding, have been shown to significantly impact the growth and medicinal yield of C. yanhusuo (Li et al., 2022). By manipulating these external conditions, it is possible to create an optimal environment that promotes higher alkaloid content in the plant.

6 Case Study

6.1 Study on the differential impact of crop rotation and flooding on yield of C.yanhusuo

Traditional cultivation methods often involve planting C. yanhusuo following crop rotation with other plants to enhance land use efficiency. However, the effects of crop rotation can be complex, potentially causing changes in plant growth and medicinal yield. Li et al. (2022) found that compared to fields rotated with peanuts, the growth and medicinal yield of C. yanhusuo were significantly improved in flooded fields (Figure 3). In flooded fields, the enrichment of Acidobacteria was found to help improve plant growth performance, whereas the enrichment of Actinobacteria in rotated fields may have inhibitory effects on the growth of C. yanhusuo.

Additionally, changes in soil physicochemical properties, such as cation exchange capacity (CEC), soil organic matter (SOM), and total nitrogen (TN), were found to significantly influence the rhizosphere microbial community, thereby indirectly affecting the growth and medicinal yield of C. yanhusuo. The study provides important references for optimizing the cultivation of C. yanhusuo and enhancing its economic benefits, particularly in selecting appropriate field management practices to promote its medicinal yield.

6.2 Study on optimizing the extraction of C. yanhusuo alkaloids based on Q-markers

The main active components of C. yanhusuo are alkaloids, which have significant analgesic, anti-inflammatory, and other pharmacological effects (Du et al., 2018). However, traditional extraction methods have limitations in terms of alkaloid extraction efficiency and purity, making it difficult to meet the demands of industrial production. Zhang et al. (2020b) optimized the extraction and purification process of C. yanhusuo alkaloids using the Q-marker uniform design method to improve extraction efficiency and active compound content.

In the study, a comprehensive scoring and uniform design approach was used, considering factors such as solvent concentration, pH, liquid-to-solid ratio, extraction time, and frequency to optimize the extraction and purification process. Through screening nine types of macroporous adsorption resins, NKA-9 resin was found to have the best separation and purification effects. Under optimal conditions, using 70% ethanol for two rounds of reflux extraction, each lasting 60 minutes, yielded a product with a total alkaloid content of over 50% (Figure 4). The study established a simple and feasible method for extracting and purifying C. yanhusuo, providing an experimental basis for its industrial production.

7 Harvesting and Post-Harvest Processing of Corydalis yanhusuo

7.1 Determining optimal harvest time

The optimal harvest time for Corydalis yanhusuo is crucial to maximize the yield and quality of its medicinal tubers. Studies have shown that the growth and medicinal yield of C. yanhusuo can be significantly influenced by the field conditions and cultivation practices. For instance, planting C. yanhusuo in previously flooded fields has been observed to increase tuber yield compared to fields used for peanut rotation or without any rotation (Li et al., 2022). Additionally, the developmental stages of the bulbs, such as bulb initiation, early enlargement, and maturation, are critical periods where the biosynthesis of alkaloids is highly active. Transcriptome analysis has revealed that alkaloid biosynthetic genes are upregulated during these stages, indicating that harvesting at the right developmental stage can enhance the alkaloid content (Liao et al., 2016; Zhao et al., 2024). Therefore, monitoring the growth stages and environmental conditions can help determine the optimal harvest time to ensure high yield and quality of C. yanhusuo tubers.

7.2 Techniques for alkaloid preservation during drying

Preserving the alkaloid content during the drying process of Corydalis yanhusuo is essential for maintaining its medicinal properties. The drying process should be carefully controlled to prevent the degradation of alkaloids. Research has shown that the use of specific drying techniques and conditions can significantly impact the preservation of alkaloids. For example, the optimal extraction and purification process for C. yanhusuo involves using 70% ethanol with specific pH conditions and refluxing times, which can be adapted for drying processes to minimize alkaloid loss (Zhang et al., 2020b). Additionally, the use of macroporous adsorption resins during the drying process can help in the separation and purification of alkaloids, ensuring that the final product retains a high concentration of these bioactive compounds. Implementing these techniques can help in preserving the medicinal efficacy of C. yanhusuo during post-harvest processing.

7.3 Quality control and standardization

Quality control and standardization are critical for ensuring the consistency and efficacy of Corydalis yanhusuo products. Various methods have been developed to evaluate the quality of C. yanhusuo based on its alkaloid content. High-performance liquid chromatography (HPLC) fingerprints, chemometrics, and correlation analysis are effective tools for assessing the quality of C. yanhusuo. These methods allow for the identification and quantification of key alkaloids, such as tetrahydropalmatine, corydaline, dehydrocorydaline, and coptisine, which are essential for the medicinal properties of C. yanhusuo (Huang et al., 2021; Yang et al., 2023). Additionally, the use of chemical fingerprints and cardioprotection efficiency studies can help in establishing a robust quality control framework (Li et al., 2017). By standardizing the alkaloid content and ensuring the consistency of the final product, manufacturers can maintain the therapeutic efficacy and safety of C. yanhusuo.

8 Concluding Remarks

The cultivation techniques employed for Corydalis yanhusuo significantly influence both the yield and quality of the tubers. For instance, the practice of rotating C. yanhusuo with peanuts has been shown to reduce the total production of tubers, whereas cultivation in previously flooded fields results in increased yields. The soil's physicochemical properties, such as cation exchange capacity (CEC), soil organic matter (SOM), total nitrogen (TN), and pH, play crucial roles in these outcomes by affecting the rhizobacteriome composition, which in turn impacts plant growth and medicinal yield. Additionally, the identification of alkaloid biosynthetic genes and their expression profiles during bulb development provides insights into the molecular mechanisms that can be targeted to enhance alkaloid content, thereby improving the medicinal quality of the tubers.

Despite the advancements in cultivation techniques, several limitations and challenges persist. One major challenge is the significant reduction in tuber yield when C. yanhusuo is rotated with peanuts, which limits the economic efficiency of this practice. Moreover, the genetic and epigenetic variations between natural and cultivated populations indicate that current cultivation methods may not fully capture the genetic diversity necessary for optimal growth and alkaloid production. The complexity of the alkaloid biosynthetic pathways and the need for comprehensive profiling and quantification of these compounds also pose significant challenges. Furthermore, the variability in alkaloid content due to different environmental and cultivation conditions complicates the standardization and quality control of the medicinal products derived from C. yanhusuo.

Future research should focus on optimizing cultivation techniques to balance yield and quality. This includes exploring alternative crop rotation strategies and soil management practices that enhance soil health and rhizobacteriome diversity without compromising tuber yield. Advances in molecular biology, such as the identification and manipulation of alkaloid biosynthetic genes, offer promising avenues for metabolic engineering to increase the production of pharmacologically active compounds. Additionally, integrating genetic and epigenetic data can inform breeding programs aimed at developing C. yanhusuo varieties with superior traits. The development of high-throughput screening methods for alkaloid profiling will also facilitate the quality control and standardization of C. yanhusuo-based medicinal products. 

Acknowledgments

The authors sincerely thank Dr. H. Li for reviewing the manuscript and providing valuable suggestions, which contributed to its improvement. Additionally, heartfelt gratitude is extended to the two anonymous peer reviewers for their comprehensive evaluation of the manuscript. 

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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