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Antioxidants

Vitamin C derivatives

Also listed as ascorbyl glucoside, sodium ascorbyl phosphate, magnesium ascorbyl phosphate, ascorbyl palmitate

Stable, gentler forms of vitamin C that don't brown or sting, but must be converted in skin and have far less evidence than pure ascorbic acid.

Limited evidenceTypical strength: About 2-10%

What it is

Because L-ascorbic acid is fragile and needs a very acidic formula, chemists attach it to a sugar (ascorbyl glucoside), a phosphate (sodium or magnesium ascorbyl phosphate) or a fatty acid (ascorbyl palmitate). These keep longer, work at a skin-friendly pH and rarely sting.

The trade-off is delivery: enzymes in skin must cut them back to ascorbic acid, and how much gets through is uncertain. In the pig-skin study that set the rules for vitamin C serums, magnesium ascorbyl phosphate and ascorbyl palmitate did not raise skin vitamin C levels at all. Ascorbyl palmitate is mostly used to protect a formula's oils.

How strong is the evidence?

Limited evidence

Evidence is mostly lab work plus a few small clinical studies, often run by ingredient makers and without placebo groups: a 10% magnesium ascorbyl phosphate cream lightened spots in about half of patients with melasma or age spots, and a 5% sodium ascorbyl phosphate lotion was reported to help acne in an open study. There are almost no head-to-head trials against L-ascorbic acid.

What it's used for, checked

Brightening and dark spots

Mixed

A 10% magnesium ascorbyl phosphate cream lightened spots in 19 of 34 patients in an older study; ascorbyl glucoside is widely used for this but has little independent trial data.

Acne

Unproven

Sodium ascorbyl phosphate kills acne bacteria in the lab and a 5% lotion helped in an open, manufacturer-run study without placebo.

Works as well as pure vitamin C

Unproven

Pure L-ascorbic acid has the stronger evidence; in the key absorption study two derivatives didn't raise skin vitamin C levels.

Suits sensitive skin

Holds up

They work near skin's normal pH, so stinging is uncommon.

Works well with

  • Niacinamide
  • Sunscreen

Who should be careful

  • Well tolerated; irritation is much less common than with pure ascorbic acid.

The studies

Every citation is checked against its PubMed record.

  1. Topical L-ascorbic acid: percutaneous absorption studies.
    Pinnell SR, Yang H, Omar M, Monteiro-Riviere N, DeBuys HV, Walker LC, et al. · Dermatologic Surgery · 2001 · Experimental (animal skin)

    L-ascorbic acid entered pig skin only when formulated below pH 3.5, with absorption maximal at 20%; skin levels saturated after three daily applications and fell with a half-life of about 4 days. Magnesium ascorbyl phosphate, ascorbyl palmitate and dehydroascorbic acid did not raise skin vitamin C levels.

  2. Inhibitory effect of magnesium L-ascorbyl-2-phosphate (VC-PMG) on melanogenesis in vitro and in vivo.
    Kameyama K, Sakai C, Kondoh S, Yonemoto K, Nishiyama S, Tagawa M, et al. · Journal of the American Academy of Dermatology · 1996 · Laboratory + clinical study

    Magnesium ascorbyl phosphate inhibited melanin formation in lab tests and reached the epidermis; a 10% cream produced significant lightening in 19 of 34 patients with melasma or age spots and in 3 of 25 with normal skin.

  3. Sodium ascorbyl phosphate shows in vitro and in vivo efficacy in the prevention and treatment of acne vulgaris.
    Klock J, Ikeno H, Ohmori K, Nishikawa T, Vollhardt J, Schehlmann V · International Journal of Cosmetic Science · 2005 · Laboratory + open clinical study

    From the ingredient's manufacturer: 1% sodium ascorbyl phosphate killed acne bacteria in the lab, a formula with it reduced UVA-induced sebum oxidation in 20 people, and a 5% lotion was rated excellent or good in 77% of 60 people with acne in an open 12-week study.