## 1 Introduction  
Citrus is one of the most widely cultivated, processed and consumed fruits throughout the world [1], with an estimated production of 98 million metric tons in 2020-2021 [2]. It produces a large number of by-products (e.g., peels or seeds) that can cause, on one hand, severe environmental pollution [1] and, on the other hand, the loss of bioactive compounds that could be key components for developing nutraceuticals and functional foods. For that reason, and to allow the recovery of these potentially bioactive compounds from agri-food by-products, the circular economy is being widely promoted [3]. Citrus fruits belong to the genus of the flowering plants of the _Rutaceae_ family, which is originally found in tropical and subtropical areas in Southeast Asia [4], whence it spread to the rest of the world [5]. Particularly, Australian finger lines (_C. australsica_ L.), commonly known as citrus caviar, are one of the seven native endemic bush species of Australia (Queensland) [6]. Due to isolation from the continent, this species evolved separately from the rest of the _Citrus_ genus, showing specific morphological and unique features, such as long ovoid contour that resembles a shape of a finger, giving it its name. There are a wide variety of peel colours ranging from dark black to yellow or green, and the almost non-existent albedo or mesocarp when compared with other citrus species. The sacs are presented in independent spherical bubbles resembling caviar eggs in different colours, depending on the cultivars, as depicted in Figure 1.  
Today, _C. australascia_ L. fruits have caught the attention of exclusive restaurants that can afford to use this special product to garnish seafood or add it to cocktails, and has even been reported to be an emerging new fruit flavour [7]. Despite very little information having been published around _C. australascia_ L., its production was estimated to be around 10 tons per annum, and is expected to rise annually [8]. Interestingly, this citrus has also infiltrated the rest of the world, and it is grown even in the Mediterranean region [9]. The trend of growing and consuming _C. australascia_ L. is forecasted to follow the same path as limes did a few decades ago, passing from being inexistent to being present in all the markets, and thereby becoming a staple fruit. Besides their economic interest, citrus fruits are one of the top preferred food flavours of the world. They are valued due to their rich nutritive profile [5], and because they are an excellent source of bioactive compounds, such as phenolic compounds, which have shown health-saltuary attributes, such as antimicrobial, antiviral, anti-inflammatory, antihypertensive or antioxidants effects [10; 11; 12]. Phenolic compounds that have been extensively reported in the citrus matrix are hesperidin, neohesperidin, narirutin, naringin, sinensistein, nobiletin and tangeretin [13; 14; 15]. Nevertheless, the chemical profile of _C. australascia_ L. needs to be studied in depth, as it may have a different chemical profile to other viruses due to its adaptability to distinct agri-environmental conditions. For instance, [PERSON] et al. have reported that _C. australascia_ L.'s peel oil composition differed from another _Citrus_ genus, except for limonoid and flavonoid derivatives [9]. A limited number of studies focused on evaluating the chemical composition of _C. australascia_ L. have identified five terphenyl esters (limonene, citronellal, isomenthone, sabinene and \(\alpha\)-phellandrene) [16; 17], four phenolic compounds (cyanidin-3-glucoside and peonidin-3-glucoside [18], vanillic and caffeic acids) [19]. Due to the novelty of the matrix and its potential interest as a source of bioactive compounds, the aims of this work were: (1) to assess the antioxidant activity and the total phenolic content (TPC) of different fractions of _C.