Skin aging is a major aesthetic concern for people, and it is produced mainly by reactive oxygen species (ROS) and proteases such as elastase, that degrade elastin. The use of natural molecules is becoming more and more common. Sargassum horridum is a brown seaweed with the potential to prevent skin aging and be a source of bioactive to develop green cosmetics. The objective of this research was to evaluate the radical scavenging ac-tivity by the 2,2-diphenyl-1-picryl-hydracyl inhibition (DPPH) and anti-elastase activity of extracts of S. horridum, as well as to describe their early phenolics and saponins profiling by dereplication. Phenolic com-pounds were extracted by conventional (CONV-SH) and ultrasound-assisted methods (UAE-SH), while saponins were obtained by conventional maceration and semi-purification with n-butanol (F-BuOH). Total phenolic content and phlorotannin content were quantified by the Folin Ciocalteu method. Antioxidant and anti-elastase activity were determined in three extracts by in vitro evaluation. CONV-SH was used to dereplicate phenolic compounds by HPLC-MS, while F-BuOH was used to dereplicate saponins by HPLC. The main results showed that the conventional method of extraction increases the yield of total phenolic, and phlorotannin contents. Anti-oxidant activity observed in three extracts was between 15 and 45 % of DPPH inhibition, and anti-elastase ac-tivity was between 15 and 30 % of inhibition. Diosgenin, a steroidal saponin, and four phenolic compounds belonging to flavonols, tyrosol, and hydroxycinnamic acid classes were identified and reported for the first time in S. horridum. These metabolites are related to anti-aging properties. The present study is the first to evaluate the potential green cosmetic applications of S. horridum from Baja California Sur. This research revealed that S. horridum is an important marine resource in Baja California Sur, Mexico, that can be used as a raw material of metabolites with antiaging properties, because it may prevent the loss of skin elasticity and photo-aging caused by ROS.