## 1 Introduction  
Family Cucurbitaceae comprises 130 genera and 800 species, including several crucial crops of high nutritive and medicinal values and increasing economic interest [1, 2]. Roots and seeds of most Cucurbitaceae members share the presence of toxic triterpenes, cucurbitacins. In contrast, their fruits are safe, edible, nutritious, and possess health-promoting effects [1, 3]. _Cucumnis sativus_ (cucumber) is a well-known species of Cucurbitaceae that is cultivated worldwide, and its fruit is edible either fresh or cooked [1; 4]; in contrast, the less famous _Lagenaria siceraria_ species (bottle gourd) is commonly used on the Indo-Pakistan subcontinent and few other countries in Europe and Africa for its nutritive and therapeutic values [5]. Aside from the macromorphological resemblance, both species are reported to exhibit anti-inflammatory, antioxidant, antimicrobial, anticancer, antihyperlipidemic, and cardioprotective activities, and are used in treatment of GIT disorders [1; 4]; additionally, fruits' extracts are involved in the treatment of skin disorders [3; 4; 6]. Previous phytochemical screening of _L. siceraria_ and _C. sativus_ indicated the presence of flavonoids, sterols, terpen, phenolic acids, saponins, and carbohydrates in both fruits, whereas alkaloids were detected in _C. sativus_[3; 4; 7].  
Despite that both bottle gourd and cucumber fruits share several common nutritional and medicinal purposes as well as their involvement in Ayurvedic and folk medicines [4; 8], few studies have reported on their metabolome heterogeneity and how the bottle gourd compares to the most famous fruit in F. Cucurbitaceae, the cucumber, as analyzed using metabolomics and chemometrics. In this study, the first comparative metabolome profiling of _L. siceraria_ and _C. sativus_ fruit crude extracts is presented as measured via high resolution-ultrahigh performance liquid chromatography coupled to mass spectrometry (HR-UPLC/MS/MS) in both ionization modes for a comprehensive overview of metabolites. HR-UPLC/MS/MS is the analytical tool of choice for rapid and sensitive monitoring of secondary metabolites due to its robustness and selectivity [9]. Identification of metabolites was aided by Global Natural Products Social molecular networking (GNPS), that allowed rapid dereplication of compounds and extrapolating tentative identification into the unknown [9; 10].  
Solid phase microextraction (SPME) of volatile constituents alongside silylation of nonvolatile compounds followed by GC/MS analyses provided insight of their aroma and nutrients profile, respectively, which affect food value and consumer preferences, likewise for the first time [11]. Owing to the complexity of the obtained datasets via GC/MS analyses, multivariate data analyses using principal component analysis (PCA) and orthogonal projection to latent structures-discriminant supervised data analysis (OPLS) were applied for the first time for samples classification and assigning discriminating metabolites for each fruit.  
The study provides new insights into the chemical composition of cucumber and the less investigated species, bottle gourd, in a comparative approach leading to the identification of several first-time-reported metabolites and classes in both species and a better rationalization of their health effects and potential application as nutraceuticalids in the future, based on such chemical profiling.