## 1 Introduction  
_Curculigo orchioides_ Gaertn is primarily distributed in Asian tropical and subtropical regions, including Southern China, Cambodia, Laos, the Philippines and Vietnam. This medicinal herb is called \"Xian Mao\" in China, \"Tien Mao\" in Vietnam and \"Kali Musli\" in India and has been utilized to promote physical strength and treat various ailments, such as back pain, enuresis and impotence [1; 2; 3]. The rhizomes of _Curculigo orchioides_ Gaertn (COG) are renowned for their medicinal properties, attributed to the presence of various bioactive compounds. In a study conducted by [PERSON] et al., (2013) [1], three phenolic glycoside compounds were isolated and identified from the rhizomes of COG, namely orcinol glucoside, orcinol-1-O-(\({}^{6}\)-O-acetyl)-\(\upalpha\)-D-glucopyranoside and curculigoside. Recently, many studies have been conducted on uncovering bioactive compounds in COG rhizomes, such as polysaccharides, saponins, phenolics and terpenoids, along with their associated biological activity [2; 3]. For example, a qualitative analysis of the phytochemicals of COG rhizomes in India indicated that saponin compounds and polyphenols were present in all petroleumether, chloroform and ethanol extracts [4]. A later study by [PERSON] et al. (2020) [5] found that COG rhizomes collected from Quang Ngai Province, Vietnam contained a total of 78.48 mg oleanolic acid equivalents/g of TSC and 196.24 mg GAE/g of TPC. Consequently, the COG rhizome is considered a promising medicinal source due to its pharmacological properties [6].  
For the recovery of bioactive compounds from plant sources, a number of studies have been conducted using a variety of methods, like Soxhlet extraction, maceration and distillation. In addition, many studies have incorporated the use of advanced techniques such as microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), enzyme-assisted extraction (EAE) and pulsed electric field stimulation to reduce the extraction time and solvent consumption while simultaneously enhancing the recovery efficiency of the desired bioactive compounds [7]. In addition to the great variations in the extraction efficiency achieved with different extraction techniques, the use of suitable solvents and technical parameters like the extraction time, temperature and amount of solvent are important factors determining the recovery of the desired compounds and the biological activity of the plant materials [7; 8].  
According to the updated literature, there is limited scientific information regarding the effective recovery of beneficial compounds from COG rhizomes. Currently, the most common methods of obtaining medicinal components from COG rhizomes include long-term soaking in alcohol or decoctions for several hours, which is traditionally applied for the preparation of Chinese herbal medicines [6]. These extraction methods usually cause the significant loss of valuable compounds due to degradation resulting from the long-term exposure to high temperatures, oxygen and light. This consequently reduces the efficiency of the obtained medicinal extracts [7]. As a result, this valuable medicinal plant remains underutilized and has not been commercialized. Hence, this research aimed to determine the optimal extraction parameters for the recovery of beneficial bioactive compounds from COG rhizomes. COG rhizomes were subjected to extraction using various solvents and different extraction conditions using the maceration technique to investigate the recovery of the total phenolic content (TPC), total saponin content (TSC) and DPPH antioxidant activity. The identified optimal conditions were further applied for ultrasound-assisted extraction in order to improve the extraction efficiency.