array_agg to array

Hello,

I have got a function with a reg expr to split chemical formulas e.g. H2O -> H2 O.

CREATE OR REPLACE FUNCTION daimon.text2sumformula(text) RETURNS text[] AS $$
    select array_agg(i::text) as e from ( select unnest( regexp_matches( $1,
'[0-9]*[A-Z][a-z]?\d*|\((?:[^()]*(?:\(.*\))?[^()]*)+\)\d+','g') ) ) i; 
$$ LANGUAGE SQL IMMUTABLE;

For H2O I get an array with {(H2),(O)}
How I can return the inner elements as text, I would like to get {H2,O} without round brackets?

Thanks

Phil